Asuka Yuuki balances a pragmatic worldview with the supernatural mysteries enveloping his childhood friend. A star athlete on the school soccer team, his skepticism toward occult rituals often clashes with peers advocating feng shui solutions. A childhood accident—striking a girl with a soccer ball—unexpectedly ignited her lasting devotion.

His dynamic with the protagonist blends protective loyalty and simmering frustration, frequently pulling him to rescue her from supernatural dangers he dismisses as unreal. This tension intensifies through a rivalry with a cunning transfer student whose relentless pursuit of the protagonist escalates into arson and sabotage. Their antagonism later matures into a rivalry tempered by mutual respect, particularly during heated soccer matches.

As the reincarnated Seiryuu of the Four Guardian Deities, Asuka belongs to a lineage bound to shield the protagonist, linked to her mystical past counterpart. His inherent rejection of supernatural logic stems from an unwavering focus on tangible reality.

Subtle shifts in his skepticism emerge as encounters with magical entities provoke less astonishment over time. Though pragmatism anchors him, his choices steadily align with guardian duties, climaxing when their bond becomes pivotal in preventing a cataclysmic breach between worlds. Allies like his soccer teammate confidant and a hotheaded comedic rival underscore his level-headedness while tracing his gradual adaptation to encroaching mysticism.