May Reason

I want to cum inside a swimsuit...and inside of buruma (gym shorts), and inside the hidden creases of school uniforms... I want to masturbate to the underwear that my older sister was just wearing, and I want to do it wearing buruma.

The main character, who can't have sex with his beloved older sister, happened upon an idea...use his sister's clothes instead! His sister in turn accepts his passions -- this is a brother and sister erotic story.

In the end, they end up fulfilling their desires in different places -- just as you might expect.