Місумі Ейїчі

Eiichi is Karen's classmate who joins the Game Club at the beginning of the series. He has short black hair. His specialty is in arcade puzzle games, but he also is able to adapt to learning new games and growing skills based on observing how others play. He says that he got into gaming because he had lost his memory when he was younger and playing block puzzles gives him a link to his past. The last episode in the anime series shows his secretive past in which he had escaped some underground organizations, and then encounters his estranged sister Riki in the finals of a game tournament.

(Source: Wikipedia)