Karin

Karin Maaka is a high school student with a rare condition called polycythemia, which causes her to produce excessive amounts of blood. This excessive blood production leads to anemia and frequent nosebleeds, prompting Karin to discreetly transfer her excess blood to random strangers, who then show improved mood and energy. Her siblings Anju and Ren assist her by manipulating the affected individuals' memories to keep her condition a secret. Complications arise when Karin's new classmate Kenta Usui becomes suspicious of her behavior and she discovers her blood reacts unusually to his presence.