Based on the erotic game by Msize.

Masaki, an ordinary male student, is filled with lust for his mother, Mitsue, but spends his days tormented by a sense of immorality. On the other hand, Miki, a childhood friend and female student who is in love with Masaki, is also worried about her relationship with him, which is not progressing. One day, Masaki finally reaches the limit of his patience and reveals his sexual desires to Mitsue, successfully receiving a hand job from her. However, Miki finds out about his abnormal mother-child relationship...

(Source: Otona Bunko, translated)