Itaru Yokoyamada (横山田 格 Yokoyamada Itaru), nicknamed Yammer (よこやん Yokoyan), is a Tin Pin fan along with his friend Shuto Dan, and the pair often play Tin Pin together. However, he is jealous of Shuto's skill, leading him to be possessed by Noise at one point during the game. In the Another Day chapter, he explains that he is extremely knowledgeable of the game, however, he actually isn't very skilled at the game. Shuto is the other way around, being a very skilled player, but doesn't actually know as much about the game itself.
He and Shooter are among the people possessed by the O-Pin that are encountered in Week 3.
The kanji for Yoko-yama-da Itaru translate literally to: Sideways, mountain, rice field, rank.