If you guys like this manga, I strongly recommend Himegoto: Juukyuusai no Seifuku, it has a similar theme with a tomboy girl and a cross-dressing boy. It's much lengthier than this series and its finish too.
The man who senpai married to is the school counselor. Also I dont think she ever got her mental illness solved btw. It's the same with the anime. She is just trying to be happy.