Shared housing is common overseas and increasingly popular in Japan. A working man and his best friend split the rent until Koharu, their adult junior from college and a younger-sister role-player, moves in a few months later simply because living together sounds fun. Gentle and always smiling, she soon starts sleeping with both men, turning the house into a carefree sex-filled home. One day, he teases her while she cooks, cuddles with her, then has sex with her after dinner. They bathe together and she gives him an underwater blowjob, yet they are not officially dating, leaving him wondering how she feels when he already likes her. Once his friend returns from work, the three drink together and inevitably launch into a 3P filled with nonstop fucking and repeated ejaculations. Labels no longer matter as long as their shared sex life stays this much fun.