I had an idea while reading snk: a tg au for yumihisu basically seiaki style – Ymir is an artificial One-Eyed Ghoul and Historia is an investigator she used to work with, what happens when they see each other again?

Are you actually asking me to write a crossover with my two favorite series????? 

I LOVE YOU NONNY-MOUSE!!!

A cloaked figure looms over the ghouls who had made mincemeat of Special Class Historia Reiss’s comrades. Historia is the last human survivor in this penthouse.

A dozen ghouls were about to attack her – this was supposed to be the end – and then this kagune-possesser – someone who must be a ghoul – appeared. But why would a ghoul defend her?

She grips her ukaku quinque with sweaty hands. But the figure does not charge her. 

Historia feels her mouth dry when the figure – the ghoul – removes her mask, a mask decorated with the same blue-and-white wings as Historia’s own quinque. 

“Y – Ymir?”

An artificial one-eyed ghoul with Ymir’s face grins at her. “Hello, Historia.”

“What – how?” Historia scrambles forward to snatch the cloaked figure, her former best friend, by her wrist. Tears cloud her vision. “Why are you here right now?!”

 Ymir seizes Historia by her shoulders. “Because I was given a second chance, and I’m not wasting it.”

“You murder people,” Historia protests. But she can’t really – she’s such a hypocrite.

“And you kill ghouls, people, whether they’re killers or not. Corpses are what we eat, not necessarily living people.” Ymir pokes Historia’s button nose.

“Ymir…”

“Is that not murder?”

“But you’re a ghoul now.” Historia’s tears spill over. 

 “So? You think I’m gonna live my life for the people who used me as an experiment? Nah, Imma live like I want! I’ll find a path forward, I swear to you.”

The hall echoes with voices of the backup CCG investigators Historia called minutes ago. They’re catching up.

Ymir drops her voice. A hint of a smile curls on her lips. “After all, I’ve still got to marry you.”

Historia’s mouth falls open. Don’t you know? Ymir has to know – she must know that Historia is a bastard of Bureau Chief Tsuneyoshi Reiss, is doomed to a short life. There’s not much more life for me.

Ymir pulls back from Historia as the backup investigators break down the door. She winks at Historia.

Historia could arrest her, could swing her quinque straight into Ymir’s heart, but she doesn’t. Instead, she swings it into her arm, so that she can’t chase after Ymir. 

Ymir grins at Historia’s decision before leaping out the window.

Historia stands there, feigning fright, feigning injury, as the investigators swarm the room. But inside, she is glowing.