Ase Nure Shoujo Misaki "Anata no Nioi de Icchau!"

The protagonist is just your everyday high school student, except for the fact that he has a stronger body odor and sweats much more than ordinary. Hence, he is greatly detested by the females.

One day after school, he comes to the locker room to retrieve the gym uniform that he forgot. There, he sees Misaki, a girl he has a crush on, masturbating while smelling his clothes.

After taking pictures for revenge against the times she made fun of him, he decides to take advantage of the situation.
”If you don't want this to be exposed, you have to do what I say.”

[Translated from Official Site]