Kindai shitei: Nyoniku no nukumori

Original title: 禁断姉弟 女肉のぬくもり

Shy Kyoko is on the verge of marrying her fiancé. Meanwhile, her younger brother Kazuo—who has a delusional obsession with his sister—plans to sabotage the wedding. However, their father suddenly passes away, and relatives rush in hoping for an inheritance, only to discover the will asks them to renounce their inheritance due to massive debts. Seeing this, Kyoko postpones her wedding and vows to protect the family home. Kazuo is delighted by the postponement, but one day, Kyoko falls and hits her head, causing her personality to undergo a drastic change...