Tough ☆ Sis

I love the "caught masturbating" trope. It's very
titillating (and often funny), and it usually leads
to a rapid escalation of the story's sexual action.
I honestly think it deserves its own tag.

I know, right? Onii-chan surprises his schlicking stepsister by barging into
her room with his dick in his hand (thus giving himself away). Her doubly-
shocked reaction is priceless.

Also, when Onii-chan leaves his room to investigate the noises from Risa's
room, he's apparently naked from the waist down, and still mindlessly fap-
ping away---which makes the whole thing even funnier.