The story begins with the unnamed protagonist recalling his death by truck, finding himself floating in a white void alongside four others. These four, intended "heroes" summoned from his world, glow and vanish, leaving him behind as an "unexpected" extra. He overhears panicked "apprentice" voices lamenting a failed summoning and an angry superior scolding them for using forbidden magic that "disturbs world order." The protagonist then falls into an unknown location.
He awakens in a vast, ancient forest, feeling a strange heaviness and observing a pervasive "black shadow" covering the trees. Realizing he's likely in an "otherworld" as per his sister's manga, he initially feels frustrated and alone. He soon discovers he can use "Purification" magic, intuitively learned from manga tropes, which dispels the black shadows and makes him feel lighter.
His first major encounter is with a large, intimidating wolf, also afflicted by the black shadow and clearly suffering. Despite his fear, the protagonist's love for animals compels him to help. He successfully purifies the wolf, removing the curse and revealing its true, beautiful form. He then uses a self-taught "Clean" magic to make its fur pristine. The wolf, now healthy and grateful, shows affection and trust, becoming his first companion and guide.
Following the wolf, the protagonist discovers he possesses enhanced physical abilities, easily scaling cliffs and running at incredible speeds without conscious effort. They enter a massive, curse-ridden cave system, the wolf's den, where the black shadows are even thicker. Inside, he discovers a horrifying pile of wolf carcasses, the source of the pack's suffering. He uses a powerful "Purification" to cleanse the mass grave, causing the dead wolves to dissipate into light. This act reveals a small pack of living wolves and a dog-like creature, all of whom he purifies and cleans, gaining their loyalty.
As they venture deeper into the cave, the protagonist develops new magical abilities: "Barrier" magic to protect his companions from the intensifying curse, and "Night Vision" and "Spatial Awareness" to navigate the darkness. He also "enhances" his barrier, which unexpectedly gains an offensive capability. They eventually confront the source of the pervasive curse: a "black, ominous rock-like mass" that emits the shadows. When the rock attacks, the protagonist's enhanced barrier automatically retaliates, shrinking the rock with spear-like light. He attempts to purify the rock directly, but its curse is too potent for a lasting effect.
From a bewildered, accidentally summoned individual, the protagonist has rapidly transformed into a powerful, albeit unwitting, mage. He has gained loyal animal companions, discovered and honed a diverse array of magical abilities, and begun to actively combat the curses plaguing this new world. His journey has shifted from mere survival to a proactive mission to cleanse and understand his surroundings.
