Isekai Meikyuu no Saishinbu wo Mezasou

Kanami finds himself in a dark corridor filled with dangerous warriors and monsters after visiting his ill sister in the hospital. He discovers he is inside a deadly 100-floor dungeon in a fantasy world, where reaching the deepest level grants a wish. He possesses newly acquired magic abilities and an unnamed skill that activates during overwhelming situations, helping him survive but affecting his emotions and mental state. A mysterious girl takes notice of him, suggesting he may have the means to return to his sister, though it remains unclear what cost may be involved.