I solved the mistery
>boing, boing
It's your erection trapped on your pants
Akane probably gave it a few taps noticing it bounced back. Also gives sense to the "lucky to catch you sleeping" part.

That's all, have a good day /bag/gsu

>>712943515
Motherly and sort of pushy. She wants to help Sensei with his burden as a teacher, ironically Sensei helped her with her own personal doubts.