Bang "JJonak" Sung-hyeon was raised in Seoul, South Korea. He recalled having a good relationship with his parents and wanting to pursue a professional gaming career from a young age. He pursued first-person shooter and fighting video games rather than schoolwork. While in high school, JJonak discovered Overwatch, the game which he would later play professionally, at a PC Bang. JJonak's name is based on the Korean phrase "쪼물락낙지", which translates to "fumbling octopus". He modeled himself on professional Overwatch player Ryu "Ryujehong" Je-hong, by studying his playstyle, game settings, and choice of computing peripherals.
JJonak professionally debuted with New York Excelsior in January 2018. The team found massive success, sitting at the no. 1 seed for most of the season. JJonak quickly became known for his skill with the hero Zenyatta, a hero in the support role who JJonak adopted a unique, very aggressive playstyle for often dealing as much damage on the hero as enemy damage players. Within two months, Kotaku described JJonak's play as the most valuable on the top-ranked team, with his Zenyatta skill having surpassed that of his role model Ryujehong. JJonak's Zenyatta playstyle was inimitable by other teams in the league's first season. While Zenyatta traditionally plays a support role on Overwatch teams, primarily healing and boosting allies and secondarily dealing damage, JJonak is known for using the character's high damage output. Zenyatta's two main abilities are orbs of harmony and discord, which can be assigned to other players to heal teammates and increase a damage multiplier on enemies, respectively. JJonak's skill with Zenyatta descends from his ability to predict enemy movements, aim with precision, and take risky moves, which altogether let him make long-distance sniper and trick shots better expected of players in damage-focused rather than support roles. For this reason, he often sidelines his team healing duties to prioritize damage. Support roles, such as those filled by Zenyatta, traditionally accompany a high-damage role as a bodyguard, but with JJonak's high-damage play, the New York Excelsior's other support player often would escort and boost JJonak. This nontraditional strategy contributed to the New York Excelsior's standout debut standings and the two support players' receiving the highest season rankings. JJonak was named the most valuable player of the league's first season by an extremely large margin, earning twice as many votes as the next closest player, Chan-Hyung “Fissure” Baek of the LA Gladiators. For this, Blizzard created a special cosmetic skin for Zenyatta inspired by JJonak's background, which was made available for players to purchase during the 2019 Overwatch League season. JJonak competed on the Atlantic Division's starting roster in the Overwatch LeagueAll-Star Weekend.
