ウチの弟マジでデカイんだけど見にこない?

Nao is a boy small in stature, but with an unusually large penis. One day, Nao's sister-in-law, Chiaki, decides to her brother's oversized penis. The two girls invited are Nagisa, a blonde-haired gal, and Yukiko, a neat, black-haired girl. The two...