RemiSaku

RemiSaku (レミ咲) is the femslash ship between Remilia Scarlet and Sakuya Izayoi from the Touhou fandom.

Canon
Sakuya is loyal to Remilia Scarlet and serves her as the Head Maid without question, a servitude in which no one knows why either trust each other so much. In Touhou: Imperishable Night, Sakuya and Remilia were partners. Sakuya follows Remilia's requests even when she knows it won't work, such as catching Lily White to restore Spring in Strange and Bright Nature Deity, as requested by her mistress. When Remilia playfully criticizes Sakuya for her failure to catch spring, she takes it in good stride and doesn't disagree. She will also do tasks for Remilia which she won't even ask, such as accompanying her in Imperishable Night and Immaterial and Missing Power (or trying to, in the latter case), or putting on a sleight-of-hand magic show for Remilia without warning in Curiosities of Lotus Asia. They are shown to be close together and share history with one another, evident by from Sakuya's story in Imperishable Night.

In Imperishable Night, Remilia offered Sakuya to become immortal so they can be together forever; however, Sakuya politely declined, opting to stay a mortal human, yet reassured her mistress that they'll "be together as long as [Sakuya] is alive." Remilia respects her maid's wishes, and the duo continue through the story.

Other characters in the Touhou universe will occasionally refer to Sakuya as the "Devil's dog", referring to the fact that Sakuya is Remilia's maid. Such as in Sakuya's route for Perfect Cherry Blossom, when Ran and Lyrica refer to Sakuya as a dog.

The name "Sakuya Izayoi" was given to Sakuya by Remilia Scarlet.

Fanon
RemiSaku is the most popular pairing for Sakuya and Remilia. In the 13th Touhou Popularity Poll (東方シリーズ人気投票 Touhou Shiriizu Ninki Touhyou), an annual survey conducted by the Japanese Touhou Wiki since 2003,  RemiSaku ranked 4th place for the "Best Partner" category with 4121 points.

Fanon works often depict Sakuya fawning over Remilia, occasionally with a nosebleed, while the latter enjoys a cup of tea. Moreover, due to canon influence, there are also many works that illustrate Sakuya wearing dog ears/tail referencing Sakuya's nickname, the Devil's dog.

Fandom
FanFiction

Sakuya/Remilia on FanFiction.net

Sakuya/Remilia on AO3

Trivia

 * Sakuya Izayoi is the only human living in the Scarlet Devil Mansion
 * The theory that was said by Akyuu claims that long ago, a young vampire hunter was training all by herself. Confident in her abilities, she decided to target the Scarlet Devil Mansion. There she saw Remilia Scarlet, who was surprisingly strong, and Remilia easily defeated her. However, Remilia wanted the girl's power for herself, so she spared her life and gave her a new name, which also gave her a completely opposite fate: Sakuya Izayoi. Sakuya then became the head maid of the Scarlet Devil Mansion before it was moved to Gensokyo.