Hitokui Magical: Satsuriku Kijutsu no Niounomiya Kyoudai

A group is invited to observe unusual research involving Kuchiha Madoka, a girl who appears to be immortal. Ii, a user of nonsense abilities, joins Ichihime Yukariki and Kasuga Kasugai to investigate at a clinic in northern Kyoto. There, they encounter the Niounomiya siblings, known as the top killers globally. The story introduces these siblings as they become involved in this strange situation.