Shi ga Futari wo Wakatsutomo
死がふたりを分かつとも
A boy named Ryuusei is saved by a demon girl, but in the process, he dies. To prevent his death, she gives him part of her power, transforming him into something like a demon. However, if they are separated, he will die. Additionally, if they fail to locate the person who originally summoned her within a year, he will also die.