Ryuichi Omiya is a fourth-year college student who meets Sora Nagase, Mire Yoshizuki, and Reika Kawatani during their train journey to Nara and Kyoto. His presence draws their attention when they notice him carrying an Onpu Segawa keyholder from the Ojamajo Doremi series, revealing him as a fellow fan. This shared interest leads Ryuichi to voluntarily join their group as a guide for exploring Nara and Kyoto, locations significant due to their appearance in school trip episodes of the original series.

During the trip, Sora Nagase develops romantic feelings for Ryuichi and confesses to him on the final day in Kyoto. Ryuichi does not reciprocate her feelings. Despite this rejection, no lasting discord arises within the group. The experience contributes to the broader theme of personal growth, as Sora and the others later reflect on their journey and resolve to move forward.

Characterized by a "pure" nature and a "slightly clumsy" demeanor, Ryuichi primarily facilitates the main characters' exploration of Ojamajo Doremi-related locations. His knowledge of the area and enthusiasm for the series aid the group's bonding, reinforcing how shared cultural touchstones foster connections. His background beyond being a college student and fan remains unspecified.

Following the events in Kyoto, Ryuichi does not appear again. His involvement is confined to the Kansai journey, and he is absent from the film's concluding segments focused on the three women opening Café MAHODO.