Dungeon Dive: Aim for the Deepest Level (Manga) Vol. 4 (manga)

One moment Kanami is visiting his sick little sister in the hospital, and the next thing he knows, he wakes up in a dark corridor full of cutthroat warriors and bloodthirsty monsters. Kanami quickly learns that he is in the 'labyrinth,' a deadly 100-floor dungeon in a fantasy world - and for those able to reach the deepest level, a wish will be granted. Kanami seems to have received magic powers and a special unnamed skill that kicks in whenever he is overwhelmed, which helps him stabilise but has a disturbing effect on his emotions and mind.

After attracting the attention of a mysterious girl, Kanami may have the power he needs to return home to his ailing sister... but at what price?