Aijima Senpai is a university student and member of Masaki Jōgasaki's film circle, where he occupies a subordinate position. He simultaneously leads a secret organization called the Secret Society Lucky Cat Chinese Restaurant. His appearance consistently features distinctive buck teeth and glasses. During the incident involving time travel to repair an air conditioner remote, Aijima arrives at the protagonists' apartment. He discovers the functional time machine and is baffled by its existence. Aijima reveals details about recent events that other characters do not initially remember, adding complexity to the disrupted timeline. When the protagonist travels back to resolve the remote incident, Aijima's glasses become an object retrieved in the final sequence.