what's that doujin where the sisters think their older brother is a pervert and then the older brother turns younger and they think he's cute and fuck him?
Sounds interesting, Bump!
>>15079481
I think this is it.
http://www.tsumino.com/Book/Info/23632/1/ane-taiken-shuukan-the-older-sister-experience-for-a-week-chapters-1-5sp