YumiHisuMika

YumiHisuMika is the poly ship between Mikasa Ackerman, Historia Reiss and Ymir from the Attack on Titan fandom.

Canon
Historia and Ymir have a deep bond, and Mikasa seems to recognize this. Back in chapter 37 of the manga, Krista’s identity as Historia Reiss is revealed, though without the name. Eren, Armin, and Mikasa immediately know who Pastor Nick is talking about, and know Krista’s the one with connections to the Wallists he is talking about. Hange doesn’t know who she is, so they describe her to them. Eren and Armin both comment on physical appearance and personality. While Mikasa says, “It’s the girl who’s always with Ymir.” She says this in response to Hange saying they haven’t gotten familiar with all the new recruits yet. Eren and Armin’s answers are a thousand times better for someone asking who they’re looking for in a battlefield. Whereas Mikasa’s is basically worthless as far as clarifying Krista’s identity. But that’s the first thing she thinks of. Not #10 in their class; not any physical descriptors. To her, Krista is the girl who’s always with Ymir, she recognizes them both as a unit.

In chapter 41, when Ymir reveals herself as the Jaw Titan, as Historia and the rest of the trainees watch Ymir fighting against the group of Titans nearly falling off the tower when Ymir transforms, she begins to cheer for Ymir telling her not to die and to break down the tower and celebrates when Ymir does so. Historia, along with the others, ride on Ymir's back and land on the ground safely. As Ymir starts getting eaten by Titans, Historia tries to make her way to her, not even caring about the fact she is stepping into a territory filled with Titans out to devour her. So when Historia does encounter a Titan, she stops dead in her tracks, terrified. In that moment, before the Titan even get to grab Historia, it gets swiftly killed by a newly arrived Mikasa. Thanks to this, Historia gets to meet Ymir  and reveals her true name to her.

After Reiner, Bertholdt and Ymir run away with Eren held hostage, Historia insists that Ymir is still on their side, and begs the other soldiers to rescue her. Later, she joins the rescue mission against Armin's advice. The team eventually manages to catch up with Reiner and Bertolt, but are unaware that Ymir has been convinced to ally with them in exchange for Historia's safety. When Ymir appears in her Titan form, Historia rushes to greet her and is swiftly ensnared in Ymir's mouth, so the Warriors can kidnap her. Mikasa, who was watching from afar, alongside Armin, Jean and Connie, stares at the whole ordeal confused and shocked. But when Jean says he never really believes she was on their side to begin with, Mikasa starts to understand the situation.

So the Survey Corps go on a mission to retreat Eren from them, and on the way there, Armin suggests that they might not be able to stop Reiner and Bertolt. Mikasa responds that they'll manage somehow and this time she'll kill them without hesitation, unlike the last time they revealed themselves as the Armored and Colossus Titan to Eren. Then she remarks that if Ymir  gets in their way, she won't be an exception either.

The soldiers follow the group on horseback and try to free Eren from Bertholdt, but Ymir interferes with their attempts. So Mikasa determines that she has to kill Ymir. She goes to kill Ymir, and Historia shouts at her to wait. Immediately, Mikasa stops. Granted, the last time someone told her to stop during an attack was against the Female Titan, and when she didn’t, there were consequences, and she’s the type who would have learned from that, but still, she stops. She stops when Historia asks her to when in the only other comparable situation, when a superior officer told her to stop, she didn’t.

Fearing that Ymir will be killed, Historia convinces her to back down, leaving the rest of the 104th free to try talking Bertolt into letting Eren go, though Mikasa is considerably less forgiving than the others. Mikasa says she has no room in her heart for that level of sympathy, and threatens to eliminate Historia as well if she continues down this path. But she looks at the two of them, and doesn’t even try to follow her threat through. Instead she hops over to perch on the Armored Titan.

The next time Mikasa and Historia are seen together, Ymir has left with Bertolt and Reiner, and Mikasa and Historia are coming back from collecting wood, seemingly by themselves. Despite their last recorded major interaction involving death threats, both of them are fine heading into the woods with just each other for company. And then, while Connie and Eren are peeling the potatoes, she and Historia are seen together again, working next to each other behind them. At that moment, the four of them start talking, and Historia defends Ymir to Connie, and Eren and Connie give each other looks. Mikasa, instead, looks at Historia understanbly.

Fanon
it's a very rare ship within the Attack on Titan fandom, with barely one work of fiction written in AO3. Although it can be seen in a romantic way, most fans of the ship like the dynamic this trio has as a team and how supportive Mikasa was of Historia and Ymir relationship due to the fact that Mikasa and Historia, though probably not aware of it, are alike in the sense that each has a person who is important to them, and each is willing to go to any length to ensure the safety and well-being of that person (Eren in Mikasa's case, and Ymir in Historia's). After Ymir's death, most fans of this ship started supporting MikaHisu seeing how close Mikasa and Historia got to one another, and how Historia herself said that Mikasa was her "perfect match".

Fandom
FAN FICTION

Variations

 * YumiHisu refers to the ship between Ymir and Historia Reiss
 * MikaHisu refers to the ship between Mikasa Ackerman and Historia Reiss
 * MikaYumi refers to the ship between Mikasa Ackerman and Ymir