There will be no sexual content in this game, no worries.
Also, there was poor wording on my part in the beginning of the game. "Picking up my brother's class" sounds as if Hayato is taking his place as a teacher, but this is not the case. Yukio, Hayato's brother, was a student in that class.
I have since updated some dialogue to make that more apparent, and will be releasing a more cleaned-up version of the game.