Kotouma Natsuki is a descendant of the Light Clan, destined to fulfill her duty as the holy warrior Splendour, defeating evil forces. She constantly fights to uphold justice, her unwavering beliefs earning her the respect of those around her. One day, she encounters Fungus, a sinister mushroom monster. Though Natsuki nearly defeats Fungus in their first battle, she allows him to escape. As a result, her classmates become infected by Fungus's mushroom spores and are attacked—and Natsuki herself becomes infected too. Trembling with rage and sorrow, she confronts Fungus once more, but again fails to stop him. Each encounter exposes her to more spores, gradually corroding her mind. Fungus realizes his spores have the power to drive humans into lustful madness, and he relentlessly assaults the corrupted Splendour until she loses consciousness. Her body, bound and crucified, is smeared with a slimy mixture of spores, marking the tragic end of her downfall.