Mr. Black debuted in Underground, where he was informed by his mother of Team Core-Tech's impending arrival at the Underground. Mr. Black greeted the team when they arrived, and explained how everything works in the Underground. Mr. Black also lied to Chase Suno about knowing anything about Jeredy Suno due to Black only having just heard Jeredy's name from his mother. Mr. Black and Spikelash then fought against Bren and Quickforce and were losing until Black revealed that he had rigged the battlefield to hold Quickforce in place and used that to his advantage to defeat Bren. Jinja then challenged Mr. Black to a fight with no Monsuno, so Black instead sent Righty and Lefty to fight Jinja, but both bodyguards were defeated. Mr. Black and his bodyguards then chased Team Core-Tech to the subway, where Black fought against Chase and Lock, but was defeated. Afterwards, Mr. Black was berated by his mother on his failure to take Team Core-Tech's Monsuno.