A/N: Anonymous on tumbler asked: for the writing prompt how about veraederung-verse where runs balance is absolutely terrible. after all, naturally he WOULD have a tail.

When Rin was young, barely eleven months old, Fujimoto was told that for all the child's incredible enthusiasm, he really could not stand on his feet for more than two seconds before overcompensating and falling flat on his face. But according to the priests, Rin would get up, tears in the corners of his eyes but a stubborn tilt to his soft jaw and his mouth set in a deep, adorable frown.

Then he would take another step, fall, and the cycle would repeat.

The slow worry didn't start until he heard after a particularly bad mission that Yukio started outstripping Rin in the walking field. Every book that Fujimoto read, en route from mission to home and home to mission, said that children developed at different rates, but this was atypical of the duo; Yukio tended to solve puzzles faster, and Rin had started crawling much sooner than Yukio had. Once Rin went to two feet however…

"Should I be worried?" he asked Mephisto over the phone just a week after the twins' first birthday, drumming his fingers against his desk. It was a rare day off from work, and he was both bouncing Yukio on his knee and watching Rin stand and fall over and over, tensed to get out of the chair at a moment's notice.

Mephisto laughed. "Oh no, Rin-kun will be fine! It will just take some time to adjust to moving differently than he's been programmed to."

"Programmed?" Fujimoto frowned and, at Yukio's insisting, set the younger twin on the floor. "These might be his children, but they did grow in their mother's womb. Unless you need to tell me something about that?"

"Oh no, no, of course not! I was simply referring to how we sealed Rin-kun's powers away—you remember the physical form he was born with!"

Fujimoto eyed Rin as he started to push himself up onto two legs, butt in the air, and slowly stood himself. "The…tail?"

"Of course! Rin-kun will find a way around it, and if he doesn't, then the whole reason we saved him was rubbish and we can move on with our lives!" Mephisto was cheery—too cheery. "Now, I need to dash! Headmaster-duties calling, my new issue of Weekly Shōnen Jump to read—the important things in life! Ja ne!"

"Wait, that's—" Fujimoto growled and rubbed at his temples as the call disconnected. Damn, sometimes talking to the guy made him really want a smoke.

He looked over at Yukio toddling to Rin's side, saw Rin start to topple over, and could swear he had some sort of future vision because fuck it all he didn't want to deal with crying children right now.

Fujimoto vaulted over the desk right as Rin fell over his own two feet into Yukio, who gave a startled cry and tipped back, thankfully, into Fujimoto's arms. They both stared up at him in confusion. Then Rin gave a grin and started laughing, erupting into baby-babble and encouraging Yukio to do the same, all stubby front teeth and gums.

Sitting back on the floor, he hefted them both into his lap and sighed. "Don't scare me like that, you damned brats."

Rin burbled and stood, pudgy hands braced on Fujimoto's knee. Almost without thinking about it, he lifted his left hand for Rin to use as a crutch. Rin stared at it, then latched both his hands around Fujimoto's palm and fingers. He laughed, and started slowly walking up from Fujimoto's knee.

"That's right," he said, Yukio warm against his other hand. "Just like that. Slow and steady, don't rush it! You've got a bit of a handicap, apparently."

Rin stopped, then swiveled his head to grin. He swayed, started to tilt forward, and Fujimoto spread his hand out further, leaning over just in case Rin fell the rest of the way. He didn't. "Easy there! Don't need any more bruised noses than you've already got."

Yukio tumbled off his knee and scooted himself to sit more against Fujimoto's inner thigh, hands slapping the floor as he did so. He raised an eyebrow at the kid—had it already been a year? Insane.

"I know you're smarter than that, but if you want to crawl, go for it I guess." Fujimoto dropped his left hand for Yukio to play with, and regretted it when Yukio pulled his fingers into his mouth and started gumming on them.

"Oh fuck that's gross," Fujimoto said, staring in distracted horror. "That's normal for babies, right? They just chew on people. Right."

He thought that's what they did, anyways. Jiborou had always laughed about soggy fingers for lunch when he came home from work, and Fujimoto hadn't been around for more than hours at a time in the past year.

Shit, it had been a year.

His hand was pushed down, and, not expecting it, he let it. Rin fell to the ground with an almighty bang! and for a moment, Fujimoto felt his heart stop.

But as Kidomarou had relayed every night without fail, Rin rolled back onto his butt, stared down at the floor with a glare that might someday burn down the world, and moved to get back up.

Despite himself, he found laughter bubbling out of his chest. "Man, if Mephisto thinks it's rubbish saving you if you can't walk, he really hasn't seen those eyes, has he?" He reached out a hand and ruffled Rin's shock of hair, surprisingly soft for a kid who tumbled around on the ground all day.

Yukio patted his stomach and gurgled something that almost sounded like Japanese, and he grinned down at him too, ruffling his fingers through Yukio's hair as well. "You're going to be a right pair, aren't you?"

Rin crawled over his leg and tumbled into Yukio, who stared at him for a solid second before bapping him on the head. Fujimoto felt another laugh startle out of him, and looked down at the two children of Satan sitting almost in his lap.

"Damn, I'm going to have to take more days off, aren't I," he said. Rin bapped Yukio on the head as well. When Yukio started to get a pissy look on his face, Fujimoto wrapped his arms around them.

"Hey hey, stop. You're the only twin each other has, so look out for each other, okay?" He put his face down near theirs. "Got it?"

For a moment, Fujimoto thought that maybe their wide eyes meant they hadn't really understood. Then they smacked him in the face in tandem, and he realized that maybe they'd caught on to more than he thought they had.