I Didn't Know My Plain Little Sister Was This Big-breasted and Lewd! ~A Horny Switch That Gets Hot When Wet~

Chisato has a little sister Chimi, she suffers from what he calls a "water curse" - One day while walking home together with Chimi, Chisato experiences Chimi's water curse first-hand. - By the time they arrived home, they are completely drenched wet. - And just as both of them walk into their home, Chimi slumps on the floor and begins touching herself. - Chisato, dumb-fooled at what is happening right in front of his eyes, can't do anything but just watch. - Was my little sister always this lewd?​