My Sister’s Friend

My sister's friend named Shino has been friends with us since we were little.

Yasuo, who's always been treated kindly by Shino, held feelings of affection towards her.
He happened to see Shino come out of the bath naked, and regarding that incident, her words to him was:
"Will you let me see you naked?"

This is a lovey-dovey story about the protagonist having sex with a sister's friend that he's had feelings for since they were little.

(Source: DMM)