Keiko was corrupted by Oikawa, who essentially planted darkness within her—and it fundamentally changed who she was. The thing is, this corruption came with a strange side effect: she developed genuine genius-level abilities. But the cost was her personality, which shifted in troubling ways.
She eventually finds her way back, though. With Daisuke and the other chosen children supporting her, Keiko manages to reclaim her sense of self and her dreams. She gets partnered with Yukimibotamon, her Digimon partner. As for what comes next, Keiko's got her sights set on running her own cake shop someday.
Content compiled by AnimeList.moe from publicly available sources.