RinYukiShi

RinYukiShi is the poly ship between Rin Okumura, Yukio Okumura and Shiemi Moriyama from the Blue Exorcist fandom.

Canon
Because Rin and Yukios' guardian, Shiro Fujimoto, kept Rin out of the world exorcists and demons, but did allow Yukio to enter it when he was young, he became the first Okumura brother that Shiemi met when they were both young. Around the time Yukio just became an exorcist and was finally allowed to go in the supply shop, that Shiemi's family runs, for the first time. As Yukio and Shiro were leaving the shop, Shiemi works up the courage to walk up to Yukio so she can give him a four-leaf clover, and after Yukio thanks he and tells Shiemi that she doesn't have to call him "teacher", she gives him the nickname "Yuki". While Rin continues to leave a normal life outside the exorcist world that Yukio kept its existence from his older twin, which includes Shiemi's existence as well, Yukio made time to talk with Shimei in passing whenever he goes to her family's shop which allowed Shiemi to develop a little crush on Yukio. During one of their conversations, Yukio tells Shiemi that he has a older twin brother.

Sometime after Rin finally learned that demons exist and that Yukio is an exorcist like their guardian was, and wanted to become one as well so he could make their biological father, Satan, pay for what he did to Shiro, Rin begins to attend Cram School where Yukio turns out to be one of his teachers. Before Rin meets Shimei, when he learned that Yukio is making a trip to the supply shop and asked his younger twin brother to take him alone.

Fanon
Because fans commonly rival RinShi with YukiShi, the poly ship between the three serves as a peaceful companies.

Fandom
FAN FICTION
 * Rin/Yukio/Shimei tag on FanFiction.net
 * Rin/Yukio/Shimei tag on FanFiction.net