IMHO, Mochikura-sensei definitely qualifies as a "Sexy Onee-san", even if for a while she doubts the level of her own sensuality. That makes Douzono-kun class himself as a Man Of Culture for seeing what others perhaps cannot see.
Consider this "match made in Hentai" to be "APPROVED!"
Desperate and a little tired...That's not a great combo when you're also horny and trying to fight back urges, esp when the other person is obviously interested in you.
Consider this "match made in Hentai" to be "APPROVED!"