So what's Umi's issue? Does she feel like inferior to Yuu, that's why she wanted to changed school, in order to avoid her? Like for instance, when Yuu defended Maki, Umi felt something like shame for not defending her friend, a friend she deliberately made, and unlike Yuu who seems at first just befriended Maki so he doesn't become lonely? Or when they played together, Umi was distant, seeing how Maki and Yuu were enjoying together, maybe she thought Yuu is stealing her friend away from her and dark thought like this made Umi feel bad?