Yumi Ishiyama is a member of Team Lyoko and a supporting protagonist in Super Smash Bros. Crossover. So far, Yumi's only major role in the series was in Season 4 where, after being freed from the villains' mind control, she helped free some of the others. Yumi reappears every now and then to assist the heroes.
Yumi's main appearance is based off her appearance in Season 4 of Code Lyoko. Her Lyoko outfit is based off her appearance in Season 4 as well.
Yumi's personality is the same as it is on Code Lyoko. Yumi is also somewhat of a lone wolf.