Boro has silver-colored wavy hair, has a small scar on the bottom left side of his chin, wears a brownish black shirt with black pants and is fair skinned.
He is a level-headed and fairly modest guy. Due to his past experiences, he is quite perceptive of the people he encounters.
Boro was conversing with his apprentices while they were sitting on the train to Train City when he suddenly noticed a blue-skinned Regular enter into their carriage, who he referred to as a "Ticket Hunter". After telling Hanool Kang to go elsewhere, he eventually engaged the blue-skinned Regular in combat and defeated him with one bisecting blow, killing the Regular. Afterwards, Boro noticed that the Regular had been using Emile prior to dying.
Just then Hanool came in saying that a strange Regular had appeared in the other carriage. Following Hanool into the carriage, Boro encountered Baam who asked if they had any Tickets as he was looking for teammates to enter the tournament. Boro asked Baam what he was talking about and Baam replied using Emile to show Boro the tournament that had been announced. Boro then asked why they should join Baam and he replied that if "they" weren't stopped, everyone aboard the Hell Express would die. Baam continued to explain why "they" needed to be stopped but Boro simply asked who "they" were only to find out that they were a group led by Baam's nemesis Rachel a new D-rank. Boro asked how a D-rank could conquer the train but was told that she was backed by FUG, which surprises him. Boro then agreed to join Baam in exchange for picking the team members; he picked Hanool and the train stewardess and they went back to the previous carriage to retrieve their Tickets. Upon reaching they saw two Regulars standing over Felix's unconscious body; Boro then told Hanool to go and retrieve the Tickets to prove he was worthy to be a Ticket Holder but is embarrassed by how weak he was when he started getting beaten up. Boro asked if it would be alright with teammates as weak as that but Baam replied it would be fine as he would take the FUG Regulars and the other Regulars were for Boro to deal with.
Eventually, Felix awakened and asked what was going on with Boro filling her in before telling her she can't come with them due to her injuries, to which she agreed with. The train stewardess commented on this and Boro made fun of her statement causing the stewardess to introduce herself as Hana Yu before detailing her dreams, which Boro put a downer on. The train then arrived at Train City and the group encountered an elevator showing various floors. As they decided which floor to go to, someone suggested the 1F Entrance floor but Boro refused saying an incredible guardian resided there, after which he pressed the button to go to the 2F Residence floor.
They ride the slow elevator upwards and Boro asked Baam whether his friends might have gone to the Entrance floor but he replied that they wouldn't have gone the wrong way, sparking Boro's suspicion. Boro and Baam then discussed Baam's history with FUG and the former asked why the latter would want to bring things up with them, with the latter replying that he had things to finish with them. Eventually they reached the Residence floor and, after seeing so many Regulars waiting around, Boro explained that they were waiting to steal Tickets and enter rooms. Just then a Regular appeared trying to scout them for "Sir Aka" but Boro intervened telling him to stop bothering his teammates. The guy, recognising Boro, politely left. The group then heads to Baam's room but are attacked by a group of Regulars with Baam instantly dispatching them, surprising everyone. Boro noted that the martial arts used looked familiar when Baam's allies come out to greet him.
Inside the room Boro muttered about the residence causing Hwa Ryun to ask him if he had boarded the Hell Express before, which he confirmed that it would be his third time. He then asked Hwa Ryun if she was the one with FUG as he had many questions but she replied that he would have to ask them later as a game was about to begin. After "The Last Seven" game is explained and the Regulars in the residential area begin fighting, Boro wondered what was happening before accusingly asking Hwa Ryun who she was with her coolly replying that she was from FUG and was a Guide. She then explained that the carnage was due to FUG wanting something that was on the train, causing Boro to wonder if they were doing "that thing" again, and finished by saying that FUG would do anything to achieve their goals. Boro then asked if she knew the enemies they would be facing and she replied that she didn't know all of them but some were new D-rank Regulars. Suddenly Ha Yura arrived and both quelled the fighting and ended the game with her presence and offer, which greatly impressed Hana Yu. Boro chewed her out and told her that there were no friends on the Hell Express before then telling Hwa Ryun that they should start talking since the game was now over. Hwa Ryun asked about his previous encounter with FUG and Boro explained his history involving a Slayer candidate leaving something on the train. He finished by saying that although he can't remember much of the experience he was sure the Slayer candidate would return to reclaim what he left.
On the day of the tournament, with Baam's team drawn against Yura's team, Boro shared his dislike of the game but nevertheless he and Hwa Ryun talked tactics and strategy with the rest of their team, with Hwa Ryun highlighting that the deciding factor would be Ha Yura's strength.
After stepping on to the field of play, Boro in the position of keeper, the "Crazy Yellow Ball" game is set up. Boro mused that the rules seemed advantageous for their team but noted that Baam was acting weird after meeting Yura and also wondered what Yura was planning considering her formation with her limited number of Tickets. The game finally got underway with Baam's team taking the lead. While the Regulars watching were impressed with Baam's skills, Boro and Rak wondered why he had a blank look on his face. On the next round of the game, Boro watched in surprise as Yura overcame Baam's reverse-flow control and wondered what was going on when Baam lost one of his Tickets to the girl. Boro continued to watch the developing game until Baam finally defeated Yura by separating her from her special suitcase.
When Ha Yura suddenly vanished and the truth of the tournament being a trap set so that Yura's allies could steal the Hell Express, the Regulars present on the field of play grouped together to make sense of the situation. After some minor confrontation, Boro quickly led the decision to work together to stop the train from being stolen, which everyone present agreed with. Aka then revealed that there was an unnavigable maze-like emergency exit they could use to catch Yura and, fortunately, Hwa Ryun appeared telling them all that she would guide them through it.
After splitting the Regulars into two teams, one to stay behind to keep the tournament running smoothly and the other to catch Yura and her allies, Boro went with the latter team alongside Aka, Baam, Moontari and Ran as they were led through the maze-like emergency exit by Hwa Ryun. As they are travelling Baam asked Boro what his relationship with Aka was and he answered, with Aka rebuking his answer immediately afterwards. The group soon made it out the maze but with the problem of the elevator being broken, they were left stuck. However, after some smart thinking from Baam, they use the elevator's pathway to make it down to the Entrance floor and, after Aka smashed the door to the Entrance area down, they encountered Ha Yura and her teammate. Giving chase to her across the chasm, Yura suddenly switched Mirotic back on, with the guardian immediately launching an engulfing blast at the Regulars, allowing Yura to escape. Baam immediately gave chase, using Hwa Ryun's guiding power to get past Mirotic, with Boro following behind them after Aka threw him across the chasm. He caught up to the two and soon engaged Hong Danhwa enabling Baam and Hwa Ryun to go after Ha Yura. Boro was initially on the back foot but, after getting used to the movements of Danhwa's sword, he quickly gained the advantage and went on to impale Danhwa with his needle.
With Danhwa incapacitated, Boro asked him why he chose to help Yura, prompting a reply regarding the Hell Train. Boro brushed off the claim, saying that the train only ran through hell. Boro then caught up to Baam and was shocked to see Daniel facing him. A confused Boro exclaimed that he couldn't be here and Daniel replied that he went to hell and returned to see "her" before running away. Baam and Boro started chasing him with the former asking the latter how he knew Daniel. Boro explained that Daniel was once his comrade that got on the train with him; however over two hundred years ago Daniel got on the train again and died. Boro wondered what was going on as well as what Daniel was planning.
Eventually Baam and Boro caught up to Daniel and Angel, with Baam briefly battling Angel's Metalfish. Just then Baam's old teammates arrived along with with Aka and Moontari. Aka then shouted at Daniel, asking the same question that Boro had asked him earlier. Daniel called it a disaster for having to see Aka and Boro again but Aka shouted that he died centuries ago trying to resurrect Roen, which Daniel then casually confirms before revealing he found a way to do so. Boro called it impossible but Daniel told them that he would bring back "that guy" and ask him to resurrect Roen. Daniel ends by calling Boro, Aka and Sachi useless before destroying the stairs leading to the platform.
Boro wondered how they were all going to get to the platform now that the stairs were destroyed but Beta arrived and told them all that he would fly up. Later on, he travels up with Beta and Ran as the former flies up to the platform using his partial ignition.
Boro appeared with Hong Danhwa and Hanool Kang on the 37th Floor. Danhwa asked him if the story he told them was true, with Hanool piping up too, and Boro replied that Hoaqin was the epitome of 'evil' before then revealing the events that happened 600 years ago on his first time on the Hell Express.
During the day, Boro and the company finally arrived at the Wooden Horse station and soon entered inside. At 10:30 PM, with just thirty minutes for the Hell Train to arrive at the station, Boro discussed with Khun, via Pocket, if his party would arrive on time to catch up with the train. At the end of the conversation, Aka arrived along with an old partner that stated the train had arrived at the Wooden Horse.
At the 'Altar' Boro, Aka and Sachi witnessed Hoaqin coming out of the train with Boro noting that he looked smaller than last time. Boro then watched in dismay as Hoaqin effortlessly decimated a large amount of the Regulars at the station.
Later, with only 10 minutes left to board the train, Boro and the company raced towards the stairs of the train but caught the attention of Hoaqin on the way. With freak lightning interrupting Hoaqin's assault, Baam, Khun, and Rak swiftly arrived on the stairs leading into the train. A brief scuffle broke out between the two sides but it was interrupted when they were all teleported to the train conductor's office. He introduced himself and then informed them about a game that would decide who would become the Slayer candidate in a month's time. At that, he teleported them away to different locations on the train.
Their group immediately encountered the guardian Yokim and they planned on taking him down until Hwa Ryun suggested that from that point onwards, Baam was to take all tests by himself in order to prepare for challenging Hoaqin. Boro then watched as Baam took on Yokim and discussed with Sachi about Baam's lack of killing intent; Baam eventually defeated Yokim and they passed the stage.
During their traversing of the train's pathways, the group eventually encountered the "god" of guardians. Boro and Sachi suggested turning back due to the guardian's fearsome reputation and power, but Baam adamantly decided to stay and challenge the "god" of guardians. At that, the guardian snatched Baam up and took him away. Boro and the others then waited for three weeks for Baam to return.
Eventually, Baam hurriedly returned and the group narrowly made it to the 4th stage in time.
Boro and the others listened to the rules of the Dallar Show and then watched as Khun coolly won the first round. During the second round game, "Transferring the sweetfish", Boro was partnered with Aka and Sachi.
Boro, like everyone else, is shocked to see Yuri on board the Train. After a break, he is seen helping others to pass the substitute test.
Boro is present at the meeting with Hwa Ryun, shocked at Baam and his team preparing to go to the Floor of Death. He decides to go with Sachi since Hoaqin will be there as well, and accompanies Baam to the Name Hunt Station in preparation. He is not named one of Viole's sidekicks by Xia Xia . When Arie Inieta begins to fight with Rak, Boro tries to stop Danhwa and Yeon from rushing over but fails. He and Sachi follow Hwa Ryun around the battle with the no-named. He arrives at the scene of their battle only to find everyone missing, and hears from Red Greymon that they're being prepared for the auction.
Upon the announcement of the auction, Boro sneaks into the floating island with Hwa Ryun, Sachi, and Novick to find and secure the hostages. They find one of the ten bosses, J.M, and quickly fight with him before watching Sachi fight Lulu and successfully finding the hostages. After resting, during Karaka and Yuri's fight outside the station, Boro and Sachi run with most of the regulars and successfully board the Hell Train once again, showing concern when Danhwa, Yihwa, and Rak did not return with Baam and Androssi.
Boro presses a buzzer to complete a very difficult train test for Baam's team. He, Baam and Aguero discuss their lack of manpower now that they're near the Floor of Death, and they wonder what happens to Wangnan's team. Hwa Ryun tells them not to be concerned about it. On the 40th floor, he and Sachi discuss the weather and what Evan could be teaching Aguero. He asks Sachi if there are any reinforcements, and Sachi tells him about Hockney. They introduce themselves to him at the station and bring him on board. Boro also learns about Hockney's painting, the Red Light. Two months later, on Floor 42, He, Sachi, and Bero Bero encounter Miseng and Cassano . He is shocked that Miseng wants to let Cassano pass through but reluctantly obliges, noting Miseng's maturity with Sachi. After passing the Floor 42 test, he praises Hockney's skills.
After Hockney refuses Sachi's offer to return to the Floor of Death, he is shocked to discover that Hockney used to live there, and startled when hearing about the Gatekeepers that guard the entrance. As he and Sachi discuss the implications of these revelations, Boro believes Rachel might be trying to use Hockney. Aguero, however, interrupts their conversation to make sure they're prepared to enter the floor.
At the entrance to the floor of death, Aguero tells Boro to jump off first into the floor, and the rest will follow if he survives. Boro is reluctant, but Hockney tells him that it's safe. Boro introduces Hockney to Khun and Baam, but wonders why Hockney is now going with them, to which Hockney replies he can find his painting there according to Emile. Boro, still scared, floats down on Aguero's lighthouse with Sachi until Sachi kicks him off and he dives into the pool of blood. Boro watches Baam and Hockney get swept up in the current and is separated from them, but he safely lands into the floor proper with the rest of the party. Hwa Ryun, however, also disappeared, causing a great deal of shock to him.
When he and his teammates face the Gatekeeper, he is impressed they could defeat it so quickly, saying it wasn't as bad as he thought despite being wary of it before. When the gatekeeper proves to be alive and they continue to fight it, however, he is impressed by Aguero's new lighthouse ability, aided by Beta's power. Aguero asks Boro to stand still and hold his needle out. Boro obliges, and Khun finishes the gatekeeper off by teleporting it using Mystery Sphere: Red Crystal to trick it into flying into Boro's needle.
When the second gatekeeper appears, Boro and the team are led down a hidden path to Gallstone Village by Ai, another Red Witch sent by Hwa Ryun. They reunite with her, and she explains to the party that she wants revenge on Hell Joe, sneaking into his castle with Aguero, Hwa Ryun, Androssi, and Irure as Yuri ignites her 13 Months as a distraction to rescue Grand de Sah. He hears Hwa Ryun's real objective is to get the ladle, and when Grand de Lee hears this and turns on the group, he runs away with his team only to meet Rachel as well.
After her defeat, Boro puts up his guard to defend against de Lee, but Beta ignites and rescues them, taking them to Hwa Ryun. Afterward, he reunites with Baam and stays behind to look after Rachel. When Baam brings Gustang, Boro puts his guard up, but is quickly pacified. Urek soon transports him and the other regulars back onto the Hell Train.
Aguero approaches Boro and Sachi to tell them about the plan to enter the Hidden Floor, though he does so cryptically to avoid having either lose their memories. Boro angers due to not understanding the hint, but later accompanies Sachi, Bero Bero, and Irure with the rest of the party. They are all sucked into the Hidden Floor when the Master Key activates.
Boro and Sachi appear in the town to meet Aguero, Hockney, and Rak dressed in coloquial garments. He welcomes Rak back, but Rak is apprehensive towards him. They inform Aguero that the village head, Dee, asked them to save the town and complete the quests but they refused. Aguero, however, enlists their help in completing the quests himself. In a nearby field, Boro helps defeat the plant monsters as part of the first quest, though he questions why they have to go through the trouble.
Back in the town, Boro is surprised at seeing the next quest's villain, a giant octopus, and is underwhelmed to learn its name is Octopus Kim. He begins to get overwhelmed by its power but rides Sachi's vines with Aguero up to the top of one of the buildings. Aguero explains to Boro that they can use his reel inventory to ensnare and catch the octopus. Boro ties down the fishing lines, but the octopus proves too fast to be tied down, and Sachi saves the group with his vines.
When the Big Breeder greets them, Boro is agitated that he has to listen to a song from the villagers instead of truly rest. Boro asks why the Big Breeder gave them a weak champion villain and finds out that it was atonement for making Octopus Kim too hard. Boro wants to defeat it, but Aguero is too suspicious to attack. As the Big Breeder summons the true villain of the level, Hockney drags Boro out of the way to safety. The group begins to fight the real villain, but it disappears with the Big Breeder before they can defeat it.
Boro and Sachi waited outside the town during Baam's meeting with Hansung Yu when giant rats appeared before them as part of the true grand quest, defeating them easily. Boro then summarizes the events thus far, including the fact that he's been to the floor before, but truly understands none of it.
When discussing their strategy for progressing, Hansung declares that Boro, Sachi, and Hockney will go to meet Khun Eduan and seek his help in finding Zahard's data, along with Batis and his daughter. He meets Khun Asencio, and watches in awe as Asencio effortlessly beats the next quest for him and his team. They journey to Data Eduan's palace, and Boro defeated his sworn enemy along the way, which happened to be a monster from a movie he saw when he was little. In the palace, he eats grapes as Eduan tells his team about how Zahard's data changed after receiving the mirror to the hidden hidden floor.
Due to the fact that Boro has managed to retain his Express Ticket for an unspecified amount of time shows that he is no pushover. Boro was able to easily take down a Regular who had managed to kill two previous Ticket holders, further supporting his high level of strength. Boro possesses a blue needle, that he seems proficient with, as well as an Arms Inventory.