Toshiue Lesson ~Mama to Oba-san to Sensei to~ by Puzzlebox - Adult Sex Game

Protagonist, Mitsuo Sawamura, refrains from the examination and asks younger sister of Anna who is the foster mother, aunt who is doing the secretary of the big company, Rika, is giving private tuition in English.
Someday, Mitsuo has the chance tempted Rika for the obscene image preserved in the personal computer to have been seen from her.
There is no Mitsuo of fascinating for the woman to refuse the temptation, as he is invited by Rika, though the world and the foot of dazzling senses are stepped into...