Seishirō Tsugumi (鶫 誠士郎, Tsugumi Seishirō) is a hitman who was raised and trained by Claude Ringheart of the Bee Hive Gang. Tsugumi is originally introduced as a male student who transfers to Chitoge Kirisaki's class and has orders to protect her from Raku Ichijō, whom he thinks forced Chitoge into having a relationship with him.

Tsugumi, although considered a side character in both the manga and anime, has several chapters and episodes dedicated to the development of her relationship with Raku