My Sexually Experienced Lil Sis Lends Me Her Pussy

Kento, who will start university life with his childhood girlfriend in a month,
has a worry that he can't tell anyone...
He has never made his partner cum.
Moreover, he can't figure out if her expressionless girlfriend, Rena feels good or not.
...At this rate, I'm going to be cuckolded, just like the stories in hentai manga...!!!
While Kento's thinking like that, one person appears in front of him—
It's his younger sister, Mao, who seems to have a lot of sex experience.

"Fuh, okay~ I'll let you graduate from having a weak dick~"
So, a horny relationship with his lil sis begins.​