Yuichi Mitsui, an ordinary college student, is currently living alone to attend college. One day, his beloved sister visits Yuichi during the summer vacation. His younger sister, who he saw for the first time in two years, has a developed a plump bust of loveliness. Besides her grownup appearence sister, Hana, is still ... a ridiculous idiot.

If she walk three steps, she will forget everything she learned, she can hardly read kanji, and she cannot operate the remote control with three or more switches. Yuichi decides to follow the thorny path in order to raise his younger sister, into a fine adult.

The only drawback of his younger sister Hana is that she is an idiot.

Yuuichi has decided to help Hana, forming her into a fine adult. But her large bust, constricted waist and tight buttocks is really testing his self-control.

Hanna is still living with her big brother Yuuichi, and her intelligence hasn’t increased, even though she has drunk a lot of milk. One day Yuichi hands a kitten cosplay costume to her…

Swimsuit, bikini armor and wedding dress.

It is hard to resist the temptations, with all the erotic costumes that his beloved sister, Hana shows off in.