Shin Ringetsu 1

Naoto Rindo knew the curse that afflicts the men in his family would stop him from having a son with any woman except a daughter of the Hizuki family. What he didn't know was that the curse could absorb his fiancee Suzu Hizuki's very soul. There's only one way to bring Suzu back: a ring that houses a piece of Suzu's mind. Naoto must charge the ring with sexual energy, and Suzu's busty younger sister Ayumi volunteers to help. As Naoto and Ayumi bring each other to orgasm after orgasm with blowjobs, paizuri, and lots of hot sex, can Ayumi hide that she wants Naoto for herself?