Aiichiro Nitori/Story

Season 1
While running with Rin Matsuoka, Rin says to Aiichiro Nitori that he didn't know there was going to be a joint practice with the Iwatobi High School Swim Club. Aiichiro tells Rin that the captain made the call, and mentions that the club's team members all have girly names. However, he immediately cuts himself off and apologizes after Rin glares at him and Aiichiro is reminded that Rin also has a girly name. When Rin asks him how he knows, Aiichiro tells him he was in the same swimming competition as them and says that the race was amazing to watch. When Rin is taken off of the Samezuka relay team by Captain Seijuro Mikoshiba, Aiichiro is the first person to approach him in order to calm him down. Although Rin is rude to him, he eventually apologizes and says he realizes that Aiichiro was simply trying to help.

Season 2
In season 2, Aiichiro is assigned a new roommate, Momotaro Mikoshiba, who will later become one of his best friends. At first, he's disappointed because he enjoyed sharing a room with Rin, but he and Momotaro become really close later on. When Momotaro's time qualifies for the Samezuka relay team and his doesn't, Aiichiro is disppointed. However, he makes a promise to himself that he will improve his swimming time so he can swim in the relay with Momo and and Rin. His skills improve with the assistance of Sosuke Yamazaki, his teammate and senior by one year.

Season 3
Aiichiro's swimming improves over time and his dedication is noticed by Rin who decides to make him the Samezuka team captain after Rin graduates. Nagisa Hazuki continues to tease Aiichiro at the start of every race they share, but now, Aiichiro takes it in stride instead of being intimidated and even, at times, counters with confidence.