Science-fiction: things like spaceships and futuristic inventions. May happen some day.
Hentai-fiction: sexy girls aroused by whatever is gross with you. Never gonna happen 
In this release, we’ve got 3 protagonists. The typical younger sister. Her older brother, a young adult, working small jobs apparently. And the sister’s classmate, who came to play, smelled the brother had poor private hygiene (me: wtf), and followed the brother to his room because that’s her ultimate fetish ┐(￣ヮ￣)┌
I was lost the moment the word “smegma” appeared, impossible to take it seriously. But, hey, it’s possible for hentai to be funny AND nicely erotic, as with this share: the girl is super hot, busty, meaty, a nice sex face, and with a 89 pages long volume there’s lots of room for plenty of varied action, from oral to all kinds of vaginal (my only regret was there was just two pages of paizuri and one with swimsuit sex ^^).
I hope this unconventional but pretty good release suits you, thanks a lot to Lewd Rider Ero! 
