I'll post my essay (yeah, I'm actually attempting to write an analytical essay on the themes of each story) summary after I'm done with Ai.
Saving the "main" heroine for last and, well, still haven't finished her story yet.
But really, really short summary:
Ryo - Boy meets girl, girl changes boy, boy challenges the world and saves the girl
Eri - Story of human relationships, trust, dependency on others and yuri