Abthura – Volume 1 follows Takashi and Yuri Sayoshi, siblings pulled from their ordinary modern lives into a city built around a single, living dungeon. Adventuring here is regulated. Floors are mapped. Risks are priced. Survival is treated like a job. Takashi adapts quickly. He learns restraint, positioning, and when not to act. Yuri does not. Her magic answers too easily — and sometimes without being asked. Bound by guild contracts and watched by officials who log every anomaly, the siblings take low-rank work meant to keep them safe. But the dungeon does not behave the way it should. Monsters show signs of growth where none should exist. Old defenses stir. And something within Yuri reacts to it. As pressure mounts, Takashi is forced into a role he never asked for: not hero, not leader — but protector. Every decision costs time, stamina, or trust. Every mistake echoes through the dungeon's narrow stone corridors. This is not a story about rising to greatness. It is about holding the line. Written in a grounded light-novel style, Abthura – Volume 1 blends slow-burn tension, tactical combat, and character-driven unease. It focuses on control rather than spectacle, responsibility rather than glory, and the quiet fear of power that answers too readily.