Not much is known about his relationship with his mother, but from the little that has been seen, Koji has a good relationship with her. His mother did not hesitate to praise and congratulate him when Koji communicated that he had managed to get accepted to U.A. High Schooll, feeling enormous joy for her son achievement.
Koji was partnered with Kyoka during the Final Exams Arc against Present Mic. Although Koji was very shy and terrified of insects, Kyoka's words and example of bravery convinced him to use his Quirk to talk to bugs of the forest. Koji carried an injured Kyoka through the forest to cross the escape gate and together they passed the exam.
Months later, on the occasion of the U.A. School Festival, Koji would be one of the students who would most encourage Jiro to sing, giving her more confidence.
As they sit next to one another, Koji and Rikido are often seen together and are partnered with each other during the Battle Trial Arc.
They both joined Team Hagakure during the Cavalry Battle in U.A. Sports Festival Arc.
They fought the League of Villains together during the U.S.J. Arc, so Koji is one of the people who knows Fumikage's weakness.
They also showed good cooperative skills with each other during the Provisional Hero License Exam.
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