Teihen Youmuin Fukushuu Sennou ~Namaiki Reijou Saimin~ (jap) by Pin-Point - Adult Sex Game

Aomisaka Academy, a storied and famous school attended only by the rich.
The protagonist, after getting fired from his previous job, finds himself working
as a lowly janitor at the school.
As a fat, middle-aged guy in his forties working at a high school,
he was naturally looked down upon by the elite student body.

Among such students, two girls were particularly harsh in their treatment of him.
Asuka Sakura, the strict, and brilliant head of the disciplinary committee,
and rich delinquent Reina Todo.

One day, while Asuka was berating him for leering at school girls,
she catches him peeping up her skirt, and she forces him to prostrate himself.
Reina then comes from behind, and gives him a big kick, and the incident gets uploaded.

He swears he'll have his revenge...and his chance comes when he happens to...