Kenta had to quit playing baseball after suffering an injury, since then he has felt useless.
One day while after home early than usual, he hears a moan coming from the second floor.
Worried that his Mother, Youko, had found his porn games, he quietly walks to his bedroom, however.
The moan is not coming from his bedroom but from Kenta's Mother, Youko's bedroom.
After peeking inside the slightly open door, Kenta sees his beloved Mama Youko, clad in a lascivious rubber suit and masturbating.
The next day the same thing happens.
Soon, Kenta realizes his mother, Youko is aware he is peeking at her and this makes his mother, Youko, even more excited.
Kenta, unable to control himself anymore, decides to tease her about it.​