Haitoku no Shoujo

Hiroko finds an attractive mansion as being a private tutor for any girl named Yuki. After drinking some tea available from Shizuka, Yuki's sister, Hiroko falls unconscious. Hiroko finds herself associated with a bed, naked.

She finds herself being sexually molested by Yuki and Shizuka - they normally use sex toys and perform various sex acts. Soon, the shocking family secret's revealed. Will Hiroko be capable of defend herself? After that get lucky and Hiroko?

Have the sexual debauchery present in sisters because they use Hiroko for their living sex toy.