Yui, who has already lost her mother, lives with her father and younger brother, Maa-kun. One day, Maa-kun is ridiculed by her friend for having no sexual knowledge. The only thing she sees is that if she doesn't teach her correct sexual knowledge for her mother, she will try to teach Ma-kun about sex herself. However, since then, Maa-kun has gotten carried away.
![HUNT-724 [Pechapai] was ridiculed for being small, so I"ll grope and make it bigger! No one in my class, whether girls or boys, pays any attention to me. The only one who talks to me is my childhood friend!! ○ Back when we were kids, she was a tomboy with](https://n1.1024cdn.sx/censored/m/70076_HUNT-724.jpg)
