S1·E4 The Rules of Buddyfight!

Gao and Drum have an argument and get mad at each other as Gao goes to school (with Drum secretly following him). There, his class is introduced to a new transfer student: Kiri Hyoryu, who is the boy that Gao saved from the group of bullies and has since then admired Gao. After school, Gao takes Kiri to the Castle Store where the Manager teaches Kiri how to Buddyfight by having him play an actual game. Both Kiri and the Manager use trial decks to fight as Gao stays by Kiri's side. With helpful teaching from both Gao and the Manager and despite being new to the game, Kiri defeats the Manager. After the battle, Kiri is congratulated by a stranger, Rouga Aragami, who goes on to tell him that winning is most important. Gao expresses his disagreement with Rouga, who takes his leave. Then, the bullies appear to challenge Gao, who is reunited with Drum and beats one of the bullies in a Buddyfight. After the bullies retreat, Gao and Drum reconcile. Elsewhere, Rouga is instructed by his superior, Magoroku Shido, to retrieve photon metal. Rouga uses his Dark Core to assume the identity of "Wolf" and calls out his buddy Armorknight Cerberus to start the mission.