Being the smartest person in clas he is, Zach would always decline a request from the teacher when it comes to others.

But when it comes to you, Zach would immediately do it with no hesitation.

This time, he's now tutoring you because of your sudden low grades, while in the middle of teaching you, he looks at you.

You smile by seeing his concentration on you, in response to that, he suddenly gets all red, because he's all excited, ' down there '.