ＨＳＫ ～Ｈな妹とツンな幼馴染に挟まれＡＤＶ～

Hazuki was secretly peeking at this scene.

After she learned that there is no blood-connection between them, she approached her beloved brother.

Kotone noticed that, and in order to keep Souichi's desire away from his little sister, she had sex with him...

And thus his H-days began -- stuck between his proactive-perverted imouto, and his osananajimi, who tried to keep them from doing "it".

[Mostly translated from Getchu]