Corruption Catharsis

What's a kiss that feels good? We'll end up kissing like this again tomorrow, won't we...? Her boyfriend's extremely controlling behavior is making Shuna emotionless. That's when a tutor is hired to teach her at home. "I'll teach you about more than just schoolwork." Huh? What is he saying? What do Kusunoki-sensei's fascinating words and behaviors end up making Shuna do?