Kyonyuu Kazoku Saimin Kazoku nandakara SEX suru no wa Atarimae yo ne | 巨乳家族催眠「家族なんだから、セックスするのは当たり前よね……」

The protagonist - Yuuichi - fails the entrance exam and is currently attending prep school. Around this time, his father, who is almost never home, remarries and his family gains new members.

The mature and alluring mother - Mifuyu, her gyaru eldest daughter - Natsuki, and subdued second daughter - Akiha. Yuuichi wants to welcome the new family, but living together with 3 women is too titillating. Together with the stress of examinations, it becomes impossible to suppress his libido.

And then, a mysterious package arrives. Inside is a strange penlight that has the ability to put anyone under hypnosis. But it can't make people do things that they don't want. Thus, Yuuchi first begins with "getting along as a family", and gradually, the orders become more extreme.

Moreover, he wants the women to bear his child in order to become a real family. Additionally, the mother daughters trio, filled with carnal desires, also begins to seek for more pleasure...