ヤリまん娘 ～俺の妹はビチビチビッチ～

The Miyamas were a happy household of five.
Eldest brother Kei, after his father's remarriage,
had adjusted to life with a new stepmother and two young stepsisters.

One day having lost his keys, Kei sneaked into the back door of the house
and spotted Shiho stealing his underwear.

He was like a deer in the headlights, but she was unflinching:
"I want sperm," she said.

Shiho moved on her big brother with purpose.
He couldn't resist. After they had sex,
he was forever caught in her web of seduction.

Can Kei keep his head on straight from now on!?

[from DLsite English]