Masashi Kusugi first appears as a popular yet arrogant classmate of Yuzu Hieda and Tadahiro Amatsu, deliberately targeting Yuzu with cutting antagonism to hinder and humiliate her.

Photographs captured by Chika Yurikasa suggest a romantic connection between Kusugi and Tadahiro, sparking confusion and speculation. This perceived relationship is ultimately exposed as a calculated deception.

Kusugi's identity is revealed as a facade for Michimune Ayatachi, an ancient sorcerer serving the dark god Yagarena. Under this guise, Michimune infiltrates the school to monitor Tadahiro and sabotage the Miko Council. His presence provides covert access for dark forces within the school, advancing their plans to exploit Tadahiro's spiritually significant left eye.

This dual role allows direct antagonism against the protagonists while preserving the illusion of an ordinary student, significantly complicating the Miko Council's mission to shield Tadahiro from supernatural threats. The ruse persists until his true allegiance is uncovered, confirming him as an antagonist dedicated to Yagarena's goal of plunging Japan into darkness.