Performed by adults in a sibling role-play. Jun has just started dating and worries that poor sexual compatibility could ruin her new relationship, so she asks the adult brother she lives with to let her practice on him. She tries one blowjob technique after another from the internet, insisting it is all for her boyfriend. He never expected to become hooked on his sister’s mouth, but what began as “practice” soon turns into nonstop sucking and sex.