My mother invites me to take a bath with her, and I hesitantly head for the bathroom. My mother, who was already in the bathtub, is of course already naked and unabashedly exposes herself. She is still as beautiful as ever, even after all these years, and I can't help but gape at her.

I gulp and stare at her. How many years has it been? The protagonist hesitates to say that it has been 10 years since his mother's casual words. The protagonist, who has always thought of his mother as the opposite sex, is unintentionally moved by her unprotected appearance...

[From official site]