"My big sister started working at a soapland—and to earn lots of money, she's decided I'll be her practice partner starting today!" An unexpected twist in sibling affection?! I never thought I'd become my sister's training tool. "Onee-chan! Your body is incredible!! Even though we're siblings, I can't stop getting hard..." My body honestly reacts against my will. And my overly sensitive sister won't stop thrusting! "Idiot, you're supposed to be my practice—how am I supposed to keep going if you make me cum?! (Haa... Haa...)"