Titan Shifters

Titan Shifters is the friendship between Ymir, Annie Leonhart, Eren Jaeger, Reiner Braun and Bertolt Hoover from the Attack on Titan fandom.

Canon
The five were all classmates and comrades into the Training Corps; and the only Titan Shifters in it. While Ymir didn't graduate into the top ten unlike the others, she still had the potential to be in it. When it was found out that Eren could transform into a Titan like them, Reiner, Bertolt and Annie were rather shocked, although it is unknown of what Ymir's reaction was. There is a possibility that she was also extremely surprised. The five weren't exactly close with each other, especially Ymir, who only formally knew Reiner and Bertolt. They still knew each other's names, and their Titan Powers starting from season two, where Reiner, Bertolt and Ymir's identities were discovered. Considering the fact that Annie was crystalized, she had never gotten to interact with all of them, and instead stayed asleep.

Unlike Eren, the others have known about their Titan Powers for a long period of time; in the original drafts, he also knew about his ability to transform. When Reiner, Bertolt, Ymir, and Eren are inside the forest, Reiner tells Bertolt about his feelings for Annie; which shocks him. Due to the fact that Reiner mentioned how much Bertolt looks at her, Eren and Ymir may also have known about his crush. Although not many similarities has been put between them, they were all transformed into titans at a young age, but only Ymir's transformation back to human was accidental.

Fanon
This ship may be popular due to their statuses at titan shifters, hence the ship name "titan shifters". Fanfictions would often feature and AU where Reiner, Ymir, Bertolt and Annie tell Eren about his powers and they all develop a friendship and understanding between each other. While Annie being in fanart with them is noticeably less welcomed, due to the interactions between the others having more screen time during the Clash of Titans arc, fans see them meeting during their times as cadets in the 104th.

Due to the fact it isn't implied in any sort that Ymir and Annie have met, fans aren't quick to ship it. After the fans who read the Junior High Manga saw that Reiner, Bertolt, Annie and Ymir all enrolled in the same academy and became friends, this ship overall has gained a bigger fanbase. In terms of friendship, Titan Shifters doesn't have any major rival ships, keeping in mind that this ship already has a few of the most fan-loved friendships in the fandom.

Fandom
DevianArt

Titan shifters by R-Daza on DeviantArt

Amino

Titans Shifters | Wiki | Attack On Titan BR on Amino (aminoapps.com)

Variations

 * BeruAni refers to the ship between Bertolt Hoover and Annie Leonhart
 * BeruYumi refers to the ship between Ymir and Bertolt Hoover
 * Ereannie refers to the ship between Eren Jaeger and Annie Leonhart
 * EreBeru refers to the ship between Bertolt Hoover and Eren Jaeger
 * EreRei refers to the ship between Eren Jaeger and Reiner Braun
 * EreYumi refers to the ship between Ymir and Eren Jaeger
 * ReiAni refers to the ship between Annie Leonhart and Reiner Braun
 * ReiBert refers to the ship between Reiner Braun and Bertolt Hoover
 * ReiYumi refers to the ship between Ymir and Reiner Braun
 * YumiAni refers to the ship between Ymir and Annie Leonhart