Mitsuko is borderline tsundere only when they were finally official. i did wish he retained his blunt personality but i think the moment he clammed is also showing how anxious he was regarding his relationship with Nana. And I feel bad for Nana since his personality morphed into being a women-pleaser. Like, it's not even portrayed to be because he respects them, but because he's terrified of them when they're angry. It's all fluff on the surface tho~ Nana, be happy.
Doutei Nana-kun Foreign Love