Koji is a regular at the Time of Eve cafe and can often be seen cuddling with Rina.
Initially, Rikuo and Masaki believe that Koji is a human and that Rina is his sex android. An accidental display of photos on Koji's phone reveals that he is involved with another woman and Rina storms off. Rikuo and Masaki find out that Koji is actually an android being used as a boyfriend for her master and that Koji is involved with Rina because she is similar to his master and he wants to use these experiences with Rina to be a better boyfriend for his master. Eventually he and Rina resolve their differences and their relationship continues.