|Kotaro Mizunuma (older brother)|
|Anime debut||Yu-Gi-Oh! VRAINS episode 61: "Despair From Darkness"|
Ryujiro Mizunuma (
Ryujiro had previously competed in a National Duel tournament.
Ryujiro, his older brother, Kotaro and three others harassed a student in a shopping district. They were stopped by Takeru Homura. Ryujiro urged his brother to just beat Takeru up, but Kotaro cited that he had dangerous eyes and the group fled. Later, Ryujiro spoke about Link VRAINS and Playmaker to one of the other gang members. He was interrogated by Takeru, who was looking for information on those topics. Kotaro intervened and Takeru left. Kotaro vowed to make Takeru pay, but Ryujiro's interaction with Takeru had given him an idea.
The group kidnapped Kiku, and sent her friend, Hana to get Takeru. When Takeru appeared, they released Kiku after Takeru agreed to Duel Ryujiro, with the wager that Takeru would become their minion if he lost. Ryujiro built up a strong defense, and though his monsters were destroyed by Takeru, he avoided taking damage and proceeded to Summon "Despair from the Dark".
|Takeru Homura||61, 63||Lose (flashback)|
- Yu-Gi-Oh! VRAINS episode 61: "Despair From Darkness"