TV-Series
Description
Manabu Kase is a human student at Ye Ran High School, childhood friends with Shinwoo and Yuna and later becoming close friends with Suyi. The group frequently gathers at the Frankenstein household. He lives with his uncle, a police officer.

Standing 157 cm tall with pale skin and brown hair that sometimes shifts to purple-blue artistically, he wears spectacles and is considered cute by peers, usually seen in his Ye Ran High uniform.

Self-conscious about his height, he bonds with Regis over their similar stature, sharing long snacks like pocky in hopes of growing taller. This shared concern leads others to initially misinterpret his interest in Regis as romantic attraction to Seira.

He possesses advanced technological skills, particularly hacking, taking great pride in this ability. He admires the expert hacker Tao as a mentor. When Tao attempts to hack police data, Manabu successfully defends it, earning Tao's respect – an action Shinwoo misinterprets as online flirting. Manabu later encounters Tao during a kidnapping incident, pleading for his safety.

Deeply valuing his friendships, he shows courage protecting others. He alerts Frankenstein during Yuna's kidnapping and confronts bullies targeting Shinwoo. He participates in group activities: visiting Frankenstein's home, playing games at PC Bangs, attending Suyi's photo shoots, and joining Shinwoo to take Raizel and Regis on a blind date.

He and his friends face multiple kidnappings by antagonists like Jake, Mari, Hammer, and the Union. During these ordeals, he often relies on friends and allies like M-21 for protection. He implores Raizel to save Tao, leading Raizel to affirm their friendship. His memories of several supernatural events are later erased.

Concerned for Raizel's declining health, he and Shinwoo prepare food for him, an errand leading to a conflict with bullies at a computer cafe resolved by Shinwoo. Suyi later reprimands them for the incident and related dishonesty.

In a flashback, he confides in Raizel about feeling his home life is emptier compared to Raizel's larger household. After major conflicts, like battles in the werewolf territory or Crombel's attacks on Seoul, he and his friends temporarily lose memories, regaining them upon reuniting with Raizel.

He does not appear in the spin-off "Rai's Adventure" but features in other side stories: walking to school with friends, forgetting his wallet during lunches, confronting harassers alongside Shinwoo, and excelling at video games with Shinwoo, where they are secretly the top-ranked players Frankenstein seeks to train Raizel.