Arikawa is a staff member of the Special Counter-Aliens Task Force, a small defense team formed after an extraterrestrial invasion. He reports to Commander Shiro within this organization, handling operational duties and fieldwork against alien threats.

He possesses an easygoing and approachable personality, differing from Shiro's stricter demeanor. This nature makes him a source of emotional support for the group. During a routine patrol, Arikawa found Kakashi, an amnesiac teenager lying alone on a hill, and brought him to the Task Force facility. Scientific tests confirmed Kakashi's unique capabilities against the aliens, leading to his recruitment.

Following Kakashi's integration, Arikawa lives with both Kakashi and Shiro in an isolated residential facility. This places him as a daily caretaker and emotional anchor for Kakashi. He provides consistent companionship to the amnesiac youth, offering comfort during psychological distress and uncertainty. His interactions show patience and concern for Kakashi's mental state as the teenager struggles with memory loss, existential doubts about his role, and fears concerning his forgotten past.

Arikawa intervenes directly in Kakashi's emotional crisis after the youth overhears distressing information and flees. During the ensuing alien confrontation, Arikawa locates Kakashi and presents critical evidence addressing his fears: revealing that Kakashi's previously inaccessible cell phone contained numerous saved voicemails from friends expressing care and concern. This action alleviates Kakashi's sense of isolation and restores his resolve to fight the alien threat.

Throughout the narrative, Arikawa maintains household routines and provides casual companionship, contributing to Kakashi's limited stability. His discovery of Kakashi initiated the central protective arrangement, and his subsequent actions sustain Kakashi's well-being within their shared living situation.