World's End Harem Vol. 16 - After World (manga)

Riku is settling into his new house, sleeping with a new housemate each night, and just when he thinks he’s getting adjusted to a new routine, his past comes calling. His older sister, Sakura, has suddenly come to visit! Just what befell them in their mysterious shared history? Meanwhile, Reito and the others engage in tense negotiations with Izanami, all in the name of finding a cure.