Elder Sister is a Futanari Slave

Yumiko and Takuya lost their parents when they were young.
Yumiko had raised Takuya herself.
Now she was married, and lived with Takuya and her husband.
Takuya felt unusual urges for her, and in his sadness over her marriage
he peeped at her through the keyhole.

Yumiko was a futanari.

Her d*ck was enormous, bigger than any man's. Takuya loved it.
One day he walked in from school and saw her jacking off out in the open.
It was too much for the confused horny teen, and he rushed at her.
It was rapture to anally f*ck his d*cksister at last.

Full color 36 page manga.