Rosiel being Kira's English teacher sounds good, and he could actually double as lit club advisor as well. I really like your more nuanced approach to Kira, I think it would work well in the setting, including the itch that something's missing.

(As far as tone, I just realized as I'm frantically canon-reviewing that the crazier and more hysterical Rosiel gets, the girlier he looks and dresses and I'm not impressed. This would not fly today.)