They started calling her "mum" as a joke.
By which, of course, they meant that Ragnarok had called her that first, sarcasm dripping out of his voice as he said, "Thanks, mum." and they'd thought it was hilarious when Maka simply rolled her eyes, grinned, and pulled Ragnarok into a hug and told him, "Anytime, kiddo."
"Yeah," Crona had said, smiling at her, "Thanks, mum."
And her face had softened, and she'd hugged them much more gently than she'd hugged Ragnarok, "Of course."
And they'd moved on from the encounter. And then, jokingly, some time later, they'd called her mum again―similar circumstances, dissimilar reaction only in that Maka merely laughed and gently knocked her head against theirs.
And then they'd said it on accident a few times, even in front of other people, and Maka had only blinked at their embarrassment afterwards each time before telling them there was no reason to be embarrassed. And the more often it happened, the more Crona did their best to believe her.
Even if Black Star made it kind of weird on occasion as he did with pretty much everything.
"She's not actually our mom, stupid," Ragnarok said, one day, "Why the hell do you keep calling her that?"
And Crona didn't have a ready answer for that, because honestly? They didn't know. They didn't know why they kept calling her "mum" when by all means she was more like a sister. She was their best friend. That was all they knew, really. They knew they loved her, and she loved them, and that they were best friends.
"I don't know," They admitted.
"You don't know?" Ragnarok pinched their cheek, hard, pulling the skin out, "What do you mean you don't know?!"
"I mean I don't know!" They batted his hand away, and they guessed that spoke to their progress over the last couple of years because they actually swatted and he actually stopped and pulled his hand back upon being swatted, "I was joking at the beginning and now I just keep saying it."
They expected Ragnarok to tell them to stop, or for him to make fun of them, but he didn't. He just bonked them on the head and tsked. And it was, like, a gentle bonk.
"Stupid," Ragnarok finally said, "What if she ends up as bad as Lady Medusa?"
"Maka wouldn't!" Crona defended, far too quickly for comfort, "Maka's not like Lady Medusa. Maka is…"
The realization hit them ― or, rather, tapped them on the shoulder.
That was why they called her that, or at least part of the reason.
Maka was his best friend, and she wasn't like Lady Medusa, and she cared about them and even about Ragnarok. She'd been the one to save their life, and they'd tried to do the same for her, but she was always the strong one. She was there for them no matter what, no matter when ― when they'd had a panic attack before an exam, she'd held them and almost made herself late for her own exam in the process. When they'd woken up crying from nightmares every night for months after the Kishin incident, she'd always come as soon as they called her, and she'd insisted they call her every time they woke up from a nightmare and didn't know what to do. When they'd been terrified because they couldn't manifest Ragnarok's sword form or get their blood to respond to their soul, crying that they didn't want to be useless, they didn't want to be weak, she'd helped them center themself and get the courage to try again.
She and Lady Medusa were very intelligent blondes, but that was all Crona thought they had in common, because Maka was so much better than Lady Medusa ever had been.
Maka was everything Lady Medusa couldn't be and never would have been.
She was sweet, and kind, and loving, and devoted. She was strong, but humble, and her very presence was soothing. She was determined and competitive and frankly kind of scary at times, but they knew she'd never hurt them unless it was completely necessary for both their safety and the safety of others.
And she was, Crona realized, closer to what a mother was supposed to be.
What they'd always been told good mothers were like.
"... Maka would make a good mom," They finally said, after a moment to process that, "Not like Lady Medusa. She'd love her kid."
Ragnarok seemed to consider that. "She's definitely a lot nicer to us. And we tried to kill her!"
Crona nodded their agreement.
"And doesn't her weapon keep joking about how she adopted us, anyway?"
"Yeah, Soul does make jokes about that."
Soul had been making those kinds of jokes (and not in a mean-spirited way!) since the Kishin incident. Always sort of cooly and gently prodding at both Maka and Crona about it, lips twisted into a wry smile as he told Maka to go take care of her "little sibling" or asked Crona if they knew where their sister was.
The first time, they'd asked what he meant, and he'd specified Maka, and that had been the end of it after they said they thought she was in the library.
It always stuck, after that.
Maka was their sister.
And now they were calling her mum…
"Maybe I should talk to him," Crona mused, and Ragnarok made a disgusted noise but ultimately didn't protest.
So they went to talk to him, because they figured he had more of a grasp on this than they did, or at least would be able to ask Maka about her grasp on it later without it seeming weird.
"It's not weird," Was what he said about it, "She's a mom friend. She gives off mom energy. Even if she's your sister or your partner she still gives off mom energy."
"A mom friend?" Ragnarok asked, making a face, "What kind of Dr. Seuss sh―"
"Black Star makes it feel weird." Crona admitted, cutting Ragnarok off and making him huff in annoyance.
Soul snorted. "Black Star makes everything feel weird. It's what he does. But he's called her mom to her face before too, so don't let him discourage you."
"Oh," Crona blinked, "Okay. So it's…"
"Totally normal, yeah."
"... Nice."
"Oh, Crona!" Said Maka, later that day, grinning at the sight of them alone, "There you are! How was your day?"
"I learned a lot of things," They said, "But it was good. How about yours?"
She wrinkled her nose, "Could have been a lot worse," She said, "But I'm glad ― and I can't believe I'm saying this ― to be off work now."
Crona couldn't help laughing. "You should take a day or two off, mum."
She smiled, but shook her head. "I couldn't, the students need me."
"And you need time off." They gently swatted her shoulder, "You can't be everybody's mother, mum, you'll burn yourself out."
"You're probably right," She agreed, after a moment, "I've got my hands full with Black Star and Ragnarok and Patty."
"And you don't have them full with me?" Crona lifted a brow, smiling anyway.
"You're a delight, thanks," She rolled her eyes, "No trouble to me at all."
Crona giggled, and Maka leaned in to give them a hug.
And Ragnarok popped on out, squinting at them both before, surprisingly, joining the hug and wrapping his arms around both of them. And Crona felt… Nice. At peace, really, with their sister-mom-friend and their weapon partner there just… Holding them.
Yeah.
This was nice.
They had a feeling the "mum" thing was going to stick, though.