A Japanese woman of Russian descent lives a peaceful life with her son.
Her husband died when her son was young, and she raised him on her own.

One day, she is seen masturbating in the bathroom by her son, and their life
together starts to change.
Things escalate quickly between them until the son's sexual desires
lead to their relationship crossing all sorts of lines.

She knows it's wrong, but she gradually loses her will to pleasure..

[From DLsite English]