- “You're the girl who saved me that day. You're the worst girl in the world.”
- — Eren to Historia
In the OVA “Distress,” Eren refuses to abandon Historia (then Krista) when she is taken hostage by thieves and is even willing to rescue her without anyone’s support. When the others agree to go with him, Eren accepts their help, and they end up saving her through teamwork.
Eren openly states that he prefers the current Historia more than the good-girl masked Krista from back then, a sentiment that makes her genuinely happy. Eren’s admiration and respect for Historia only deepen when she defies Rod by throwing him to the ground. Historia tries to rescue Eren because she can not stand to hear him crying about his worthlessness. This marks an important event for both Eren and Historia, as this is the first time we get to see a more "selfish" and confident side of Historia, which Eren himself admired. Eren even mentions this event when telling Historia about his rumbling plan, mentioning about how she chose to save him that day.
When Eren suggests allowing himself to get eaten by Rod, Historia instantly puts this idea to rest by outlining all the problems surrounding it. She then comforts Eren about his father, explaining that Grisha had to take the Reiss family’s founding titan for humanity’s good.
Eren later thinks about how strong Historia has become when talking to Erwin and fighting for her right to settle her fate.
Two months later, Eren speaks fondly of Historia while Jean and Armin, including him, watch her scold some kids at her orphanage. As the two are walking together, Eren remarks on how amazing Historia is, which makes her softly blush. Soon after, a jealous Mikasa interrupts them with a dark expression on her face as she does not want Eren getting too close to Historia.
Historia is the only person, aside from Floch, who knows Eren’s real intention to unleash The Rumbling for the Eldian’s freedom. Before that, she was grateful to Eren for helping them improve Paradisian in The Wall. When she hears his intention to destroy the world, Historia begs him not to do that since many innocent people are outside The Wall. Historia felt that she could not live with herself if she did not do everything in her power to stop him. Eren then suggested using the Founding Titan’s abilities to manipulate her memories if enduring them would be too much for her, but believed she could stay quiet until his plan came to pass since she, as Eren quoted, is the worst girl in the world—a phrase she described herself back when her father kidnaped them—who saved him. The flashback ended with Historia asking him about his thoughts of her having a child, leaving it ambiguous whether her unborn child is indeed Eren’s child or a child from another man.
Some people have also thought chapter 134 implied that the father of the unborn child of Historia could be Eren, as she is giving birth earlier than expected, which does not fit with what Levi said. This was just baseles speculation as in Chapter 139 the father is revealed to be the Farmer not Eren.
Some fans have noticed certain parallels between Eren and Historia (e.g. both witnessed their mothers’ deaths, both were used by their fathers). These parallels seem to connect them uniquely. Yet, this is rather insignificant considering it is ymir who was specifically written as a parallel to Historia.
With Eren being the founding titan and Historia possessing Royal blood, the two of them together could potentially be the key to saving Eldia. In addition to this, a lot of fans speculated Eren to be the father of Historia's child which increased the popularity of the ship as well as created many theories among the fanbase, although this was proven to be false later on. They both also have an interesting dynamic and respect each other.
The ship currently rivals EreMika and YumiHisu which are both canon and preferred by the majority of the fandom. Fan wars between these ships are common. EreHisu tends to get backlash due to the high possibility that Historia is in fact a lesbian, and that she is canonically queer.
- One of the official Attack on Titan card deck showed EreHisu’s card, where Eren represents the King of Clubs deck while Historia, the Queen of Hearts deck. The King of Clubs represents spiritually-mindness, argumentative, and aggressiveness. They need to work in association with others, exchange ideas, learn in discussions, and succeed in making agreements and unions, fitting with Eren’s character. While the Queen of Hearts represents beauty, magnetism, affection, and idealism, fitting with Historia’s character as the Queen of Paradis.
- In the fake previews in the Volumes for Attack on Titan, it is shown that Historia might have a crush on Eren. The main plot of Attack on Titan takes place in different universes, while the fake previews take place in modern times.