Josou de Sennyuu! Futanari Senmon Esute ~Ochitara Ikenai Gokujou Massage~

To preserve his school's strict regulations, the disciplinary committee chairman protagonist
cross-dresses, and infiltrates a certain massage parlor where students are rumored to be working.
However, he ends up receiving a free trial massage from the manager, and soon,
he can't hide his boner...

[From DLsite English]