HiroAki

HiroAki is the slash ship between Hiroomi Nase and Akihito Kanbara from the Beyond the Boundary fandom.

Canon
Hiroomi calls Akihito "Akkey" and frequently sticks his hands under the latter's armpits to "keep them warm," much to Akihito's embarrassment and annoyance. They're also both known perverts, mainly Hiroomi.

In Beyond the Boundary: Daybreak(also known as Episode 0), Hiroomi is sent by his sister, Izumi, to kill or capture Akihito Kanbara because he's a half-shade. They start off on a bad foot since Hiroomi attacks Akihito and then tries to physically drag him back to the Nase household. They are interrupted when Miroku attacks Akihito and Mitsuki, Hiroomi protects them with a glaciate barrier, which leaves him open for other attacks. Akihito takes the hit for Hiroomi and as a result from the massive damage, his shade half takes over and he becomes feral. In his feral state, he has no control over his actions and ends up nearly killing Hiroomi by literally shredding his back, despite this, Hiroomi still vows to protect Akihito.

When Hiroomi is severely injured by the Hollow Shadow and his dreamshade-side threatens to take over again, Hiroomi stands next to Akihiro, telling him how the latter might not survive(they technically can't kill him but can permanently contain Akkey), Hiroomi looks sad and dejected when he says this. Hiroomi and some other Spirit World Warriors arrive to help contain him, but Akihiro breaks out anyway. They are at the lantern festival together even though the festival is usually strictly for couples. Mitsuki fills her brother's phone with men moaning audio instead of music. Hiroomi tries to force Akihito to listen to it while they're walking, with Akihito protesting that he didn't want to listen to it.

When Mirai thinks Akihito has a girl over at his house, she starts listing off people that it could be. For some reason, she lists Hiroomi as one of them, saying how they were "sticking more than just hands in his armpits.

Hiroomi appears when the Beyond the Horizon dreamshade reveals what Akihito's weakest point is. This might not have any correlation to anything romantic, but it implies that Akihito felt guilty enough for almost killing Hiroomi that a supernatural entity considered it his strongest weakness.

In the end credits of the movie, Akihito, Mirai, Hiroomi, and Mitsuki meet each other again. Hiroomi comes flying at Akihito, knocking both of them to the ground. Hiroomi is crying, and Akihito immediately softens when he sees Hiroomi crying. Akihito smiles, showing that he also missed Hiroomi.

Moments

 * Sharing an umbrella. (Ep 6, in a flashback)
 * Talking in sync.
 * Being perverts together.
 * Calling each other out for being perverts.
 * Sharing earphones.
 * Hiroomi concerned when Akihito falls "ill" and when he is fighting the Beyond the Horizon dreamshade.

Fanon
The ship first came to be when Hiroomi was first introduced and stuck his hands under Akihito's armpits to keep them warm. It became more and more popular as the show progressed and their pasts were revealed. Their similarities and compatibility fueled the ship.

Akihiro struggles to accept his dreamshade-half and Hiroomi helps him. Fans will also play around with Hiroomi being sensitive to the cold and Akihito being warm all the time, making some cuddly and/or cute fanworks of the two.

It is the most written ship for Hiroomi and Akihito on AO3.

Fandom
FAN FICTION 

TUMBLR 

Trivia

 * Hiroomi's abilities is responsible for his sensitivity to cold, he mentions that Akihito is warm.