Sarah Adiemus is one of Yakumo Tsukamoto's best friends. She is also in the same class as Yakumo. She is from England, and she seems to know more Japanese than Eri Sawachika. She is a member of the Tea Club.
Sarah's main role in the story is supporting Yakumo, both with her problems and love life. She first appeared in Chapter B03 in the manga, and Episode 04 on the TV series. Sarah has her own cover of manga volume 9, and her image album #7. She also appears on the jackets of volumes 4 and 7 of the manga, though not on the front cover.
Sarah has many part time jobs when she is not in school. She works as a nun at a local church, playing the Organ, babysitting children, and other various church services. She is also able to perform exorcisms. She asked Yakumo to help her do a virtual wedding so she can take pictures for the Church's wedding services. Her position may preclude her pursuing romantic relationships, but at least one hopeful student has expressed interest in her, and, as she reveals in a conversation with Akira, she may have her eye on someone herself.
Aside from being a Sister, Sarah also works with Hiroyoshi Aso at a Chinese Restaurant, cooking and waiting tables.
Sarah works closely with Aso at the Chinese Restaurant, and has cheered for him at the Sports Festival. Sarah has exhibited a romantic interest in Aso much to the disappointment of Ryuuhei Suga.
Yakumo is Sarah's only known friend. Sarah first became Yakumo's friend by chance in a rather unconventional way. Their relationship began with Yakumo chasing her cat Iori around the School grounds. When Yakumo finally caught up to Iori, she became threatened by a large ferocious dog. Sarah, who at that point was a bystander, intervened by jumping in-between Yakumo and the dog. She then removed her jacket and began to bark, parrying the dog with "woofs" and jacket flails. This instantly formed a lasting bond between the two characters. The history of how Sarah became Yakumo's friend is illustrated in the first Episode of the OVA.
According to side chapter 42 in the manga, Sarah was raised in an orphanage.