Hajimete no Aku

In the spring of Kyoko's first year in high school, Eiko, a girl like a sister to her, returns with her younger brother, Jiro. The return isn't that big of a deal, but Jiro (self-proclaimed super mad scientist) has it in his head that he wants to operate on Kyoko! And, what's even more, the two of them are actually high ranking members of an evil organization on the run from the heroes of justice!

As if high school didn't have enough problems already, now she has to deal with these two living with her.