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?​