Risu is directly connected to the mystery of Caiman's altered head and missing memories.
The man inside Caiman's throat tells Matsumura that he is not the one; Caiman later remembers the name Risu, while Risu's revived head is identified a...
En attempts to control Risu as an information source, while Risu resists and escapes.
En revives Risu's head, places it on a mechanical body, and interrogates him; Risu then escapes when En's magic causes confusion.
Risu functions as the witness through whom En approaches the central mystery.
En uses Risu's revived head to investigate the person who cast magic on Caiman, while Risu possesses information connected to Caiman's identity.
Nikaido treats Risu as someone who must be removed from En's custody rather than as an enemy.
Nikaido tries to abduct Risu from En's control, punches En during the attempt, and helps create the opportunity for Risu to escape.
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