|Played by||Yoshiyuki Yamaguchi|
Yumioka as an actor wants to make good impressions on people he has eyes for, attempting to look and act cool around others. When pushed over the edge however, he can be rather immature.
Yumioka was among the male guests at a dating party started by Seiji Hayami. Unlike the other guests who payed more attention to either Honey Kisaragi or Yuki Kenmochi, Yumioka was mainly aiming for Miki. Miki had to threaten him off when Yumioka got in the way of some conversations. He was later affected by a liquid nitrogen laced drink but managed to survive and thaw out. When the restaurant they were in turned out to be filled with Panther Claw combatants, Seiji got all of the male guests out for the Flash Girls to fight them.