The Angel in the Christmas (S01E04)

When Itsuki and Chitose visit Amane's apartment for a Christmas party only to discover that the angel Mahiru lives next door, they instantly become very curious about the relationship. Chitose, obsessed with cuteness, insists on becoming friends with Mahiru. The day after Christmas, Amane notices that Mahiru has a fever. Despite Mahiru's stubbornness, Amane convinces her to stay and rest in his room. When Mahiru sees Amane so diligently taking care of her as if returning the favor she did for him that one memorable day, it seems to put her at ease. (Crunchyroll)