Habits can be a dangerous thing.

It was a reasonably nice day in Rome, and despite having studied and lived in Europe for several years, Shiro's half-awake body automatically assumed walking along the left side of the hallway, like he would in Japan.

Which is problematic if you cut a corner and someone else is walking on the right.

His pleasant musings about what to have for lunch were rudely interrupted by a sudden collision with a white pillar. No, not a pillar. It was softer (be it only slightly), and pillars don't go "oompf" when you bump into them.
Nor do they give you a death glare while rubbing their stomach and re-adjusting their attire.

"Whether that was a deliberate tackle or an attempt at functioning like a regular human adult, it was a failure of both."
Mephisto smoothed out and tucked in his mildly ruffled cravat and gave him a disapproving look. "In fact I'd go as far that even when immobile you fail at the latter. Is that tooth paste on your collar?"

"Shut up. You're lucky I wasn't carrying coffee."

That statement made the demon tilt his head to the side, examining his sloppy appearance a bit further and scanning his expression until the irked eyebrows settled in neutral mode over half-mast eyes.

"Coffee? Is it that bad?"

Shiro groaned and stroked through his unkempt hair.
"You don't know the half of it. I can hardly even remember what my bed looks like. Schedule's been insane. Even my days off aren't really days off anymore, just days of catching up on household chores, writing mission reports and judging homework assignments."

"Mmh~" The headmaster murmured, stroking his beard in thought: and then, with a slight twitch in his ears, an Idea announced itself. "What you need, my friend, is a holiday."

"No shit," Shiro huffed, stuffing his hands in his pockets. "'Cept I don't have time for one. Everyone's tugging at my robes. Shiro do this, Shiro do that... Fujimoto-sensei-could-you-please-help-me-with-whatever-minor-task-I-could-totally-handle-myself-if-I-actually-used-my-brain-for-once..."

"Oh but it doesn't have to be a long one! In fact, studies have shown that it is much more beneficial for one's health to go on several short trips over a period of time than just a single long one."

Gloved palms pressed together in front of his chest, a toothy smile coming on, eyes glimmering... Shiro recognized the pose without consciously registering it: A proposition. He straightened up a bit, guarded but curious.

"...And since, surely because of our busy schedules, it's been a while since we've done something fun together~"

Shiro grinned. Of course. Leave it to a demon to find the perfect excuse to ignore any pressing duties. This ought to be good.

"Hmmm~ You're right." He cocked his head. "Anything special you have in mind?"

"I was thinking we could take this opportunity to visit Tokyo."

What? Tokyo? Shiro frowned. The eager look in his friend's eyes didn't quite match up with something so... mundane.

"Why Tokyo? Is there something special going o-"

Realization hit him like a bus. He had seen the posters back home. The advertisements in the newspaper.

Exorcist reflexes kicking in against this sudden threat. "NO."

A few steps back, bent knees ready to run and a finger pointed at Mephisto's face like a gun. "Nononononononoyou are NOT dragging me to Comiket again!"

From ears to shoulders to the corners of his mouth, Mephisto's features instantly drooped; it was, Shiro had to admit, almost endearing. Especially when paired with the big, teary eyes. Instant moe-mode was a skill he had cultivated thoroughly – sadly, the effect of it on a demon was nothing but comical.

"But Shiro-pooooon~" he whined.

"Don't call me Shiro-pon, idiot."

He tried to turn his back and walk away, but Mephisto (when did he get this close?) nudged his shoulder against his, curving his body and neck sideways to rub the top of his head against his temple.

"Pretty pleeeease~?"

A group of glergymen edged past on the other side of the ancient corridor in a not entirely convincing display of Everything Is Normal.

"There is nothing pretty about your pleas." He shrugged the demon off and swiped the greenish curl away before it could get tangled up in the strings of his glasses. "And puppy eyes ain't gonna help."

A thought.
A poof, and the little white dog was gingerly hopping on the floor in front of him, all waggy tail and fluffy paws, looking at the exorcist and yipping.

Shiro caught his jaw and reminded himself just in time to maintain his steely resolve. He straightened his back, opening his mouth for a snappy response and-

the dog rolled over, exposing his fluffy belly, wriggling on his back, beckoning with his paws, and making little high-pitched, wailing noises, eyes still fixed.

Shiro stared...

And burst out laughing. Snickering, he put one hand at his side, the other pinching the bridge of his nose.

"My God, you're such a slut."

"Is that a yes?" the nasal voice asked from below.

"Egh, fine..."

He chuckled, and a content Mephisto poofed back into human form.

Shiro looked at the way-too-happy face and raised a warning finger: "But you pay the entrance fee, and I will NOT carry your bags or stand in any lines for autographs of people I don't even know."

That dulled his friend's enthusiasm a bit, and the gleeful look made place for a more businessmanly kind of expression.

"Fine, but then you're cosplaying."

"Not in a million years." Shiro folded his arms and Mephisto's ears dipped lower.

"And if I allow you to choose your own character?"

"Do I count as a character?"

"No."

"In that case you can forget about it." He turned around and started to walk off.

Slowly.

Wait for itttt~

Disgruntled noises of inner struggle behind his back, followed by a sudden snarl:
"I'll make it a paid day off!"

Bull's-eye. Shiro cast a wide grin over his shoulder.

"Ohhh now THAT was a major mistake for someone who claims to be a tactician, Sammy..."

He swung one leg around the other, aligning himself once more face-to-face with Mephisto, and assumed a slow, confident strut towards him, the sound of his boots echoing over the marble floor.

"Throwing money at a problem? Now I know you're desperate."

He stopped inches in front of the other and put his feet apart, ready to take a stand.

"Paid day off, you pay the entrance fee, I will carry only one, medium-sized bag, nothing more, and will stand in line with you but not for you."

Oh, that feeling. That moment when he once more succeeded to pierce that familiar, well-groomed façade and poke the demon beneath it. To witness that struggle of manners trying to reel back the rage and insult bubbling up to the surface. Worth it. Worth it every time.

"You'll sit through the panel Q&A with me." Mephisto's crossed arms left no room for compromise.

"Fine, but I want to watch at least one cosplay competition," Shiro countered.

"I get to pick the schedule."

"I get to pick the game demos."

"Photobooth."

"Free lunch."

"Cat ears."

Red and green irises locked each other like battling laser beams. Had this been an anime there would have been sparks.

Finally, Shiro shifted his weight backwards just the tiniest bit. Defensive.

"No pictures. No illustrations. No hijacking of the convention security cameras, no recordings of any kind, got it?"

The thin eyebrows performed an intricate display of acrobatics in illustration of the turmoil inside the demon's head, trying to figure out a way around this rule. Judging by the way his jaw clenched more and more with each passing second, there wasn't one. Much to Shiro's delight.

"Grmbl... Fine."

Still slightly irritated, Mephisto offered his hand. Shiro hesitated for a second... But then shook it.

"Deal."

"Ordeal, you mean." The demon sighed, brushing imaginary dust off his lapels. "Why you insist on turning this into such a drama every year is beyond me."

Shiro dug up a cigarette from his pockets and put it in the corner of his mouth while looking for his lighter.

"I thought her majesty enjoyed drama."

Ah, there it was. He turned the small metal box over in his hand and flicked it open. Mephisto huffed.

"To watch, yes. Not to participate in." A sideways look. "You're not going to smoke indoors, are you?"

"Do you see a prohibition sign anywhere, princess?" he asked while cupping a hand around his cig and clicking the lighter.

"I certainly don't see any endorsement either."

"Yes you do." He took a leisurely drag and teasingly blew the smoke towards the disgusted demon. "Me, right here. I'm endorsing."

"I ought to have your doctor's license revoked."

Shiro laughed.
"What, because demons won't like me? My, what a tragedy!" He blew a whiff towards a bobbing coal tar, which immediately changed its course to a less unpleasant direction.

Mephisto pulled an affronted face, but then the corners of his mouth turned upwards.
"As long as you realize you're only allowed to light those awful cancer sticks of yours in the designated, restricted areas at Comiket."

Shiro almost dropped the cigarette.

"WHAT? Why?!"

What used to be slight amusement became a full-blown sadistic grin.

"Fire safety issues. You might want to start practising withdrawal - last time the waiting line for the entrance lasted 3 hours."

With a flamboyant turn and a supremely irritating, finger-wiggling wave, he bade the exorcist farewell:

"Ta-tah, Shiro-Pon~"


Author notes:

I assumed Shiro to have had at least the better part of his priest education and ordination in the Vatican, because
a) he would have visited there all the time anyway
b) Catholism isn't a big thing in Japan, despite what anime would have us believe
and
c) he seems to have picked up some Western habits: When he beckons Rin over in chapter one of the manga/ episode one of the anime, he does so in the European fashion, palm upward. In (most of) Asia, they beckon like the famous Chinese beckoning cats: Palm down, which to Westerners seems more like waving or shoo-ing. To firmly imprint something like that to the point where he uses it even in Japan, he should have spent a significant amount of time immersed in Western culture.

About coffee: This is a headcanon I picked up from Superior Dimwit. Shiro doesn't like coffee, he prefers tea (and hard liquor).