Shoutout to the Anon on Tumblr who requested this. Call it my Christmas gift from me to you, and anyone else who follows me because of my YGO fics. Stay safe and happy, and have a great holiday, no matter what you celebrate xx
As this kind of stuff between siblings often does, it had started innocently enough. Because the brothers had grown up together, they were privy to things about one another that no one else in the world knew; but as a general rule, they each tried to not exploit this privilege as a sign of love and respect. But some things, however, were just too good.
For instance, it was no secret that Seto could be a little, well, grumpy. He worked long, gruelling hours in a high-stress job, and still had to find time to raise a child and deal with a seemingly neverending onslaught of supernatural garbage. All things considered, it was no wonder that he'd never win a prize for being the cheeriest guy in the room.
However, there were ways and means to make even him smile, and Mokuba knew them all. But perhaps the quickest and most effective way to elicit a laugh out of the straight-laced businessman was something Seto would sooner relinquish his duelling deck than reveal.
Seto Kaiba was, in fact, extremely ticklish.
Mokuba had no choice but to conclude that it was a family trait because he, too, was prone to squirming and giggling at the right kind of touch; but his brother was definitely the more sensitive one.
The entire ordeal began one seemingly ordinary evening. It was getting close to that time of the day where Seto packed up for the night and left work, only to go home and probably work some more. It was hot in his office, as the weather outside was warm and the air conditioning system was down for some kind of repairs; so, since there was nearly no one else in the building, Seto didn't seem to have a problem with shedding his heavy boots and long, domineering jacket to combat the temperature. Only his brother was around to see him, as most everyone else had gone home.
He was just wrapping up a rather frustrating conference call, where his associate on the other line seemed to be doing everything in his power to irritate him – and Seto had already been in a bad mood from events earlier in the day. Coupled with the heat, he was a groaning, fuming mess.
Mokuba, who didn't have school or anywhere else important to be that day, decided to do something to brighten him up a little. While Seto was preoccupied rubbing his eyes as though doing so could remove the headache all this stress was causing, Mokuba silently crawled under the desk and tickled the bare sole of his foot.
Seto yelped and tried to pull away, but Mokuba's grip on his ankle was firm and he couldn't jerk around too much without kicking his brother in the face. So instead he wiggled in his seat, trying to pull back with all his strength.
"St-stop!" He attempted to sound angry, but it was very difficult to do when he was laughing so hard. "I mean it, Mokuba, cut it out!"
By this point, Mokuba was laughing too, and it was a nice sound to be echoing around the large office. When the younger was satisfied that he'd successfully cheered up his older brother, he let him go and climbed out from under the desk.
Seto took a deep breath to calm himself and glared at Mokuba. "Don't ever do that to me again," he ordered.
Though his tone was firm, Mokuba wasn't deterred in the slightest. "I won't promise a thing."
Despite the wording, it wasn't at all about promise. It was a challenge. Mokuba turned away and asked something about whether they were going home soon, and what would be for dessert.
Alright, little brother, Seto thought to himself, smirking. He never could back down from a challenge, even one set by Mokuba. You're on.
Seto rose from his seat, quietly snuck up behind Mokuba and grabbed him so suddenly he jumped – but he didn't give the boy enough time to pull away before drumming his fingers up and down his sides, where he knew he was the most ticklish.
Mokuba squealed and squirmed, trying and failing to escape his older brother, who was a good deal stronger than him.
"S-Seto! Don't!" He kicked his legs, reaching for anything he could use to get away, but he found nothing. So instead, he decided to fight back.
Mokuba tickled Seto under his arm, earning himself just enough time to flee. He bolted from the office, still in stitches. He didn't need to look back to know Seto was hot on his heels. He ran through the deserted hallways, past empty offices and barren conference rooms, and wound up in reception.
With very little thought, and almost no kind of plan, he hid behind a chair until Seto caught up, and when the elder looked around for him, Mokuba launched himself out of his hiding place and tackled Seto to the ground.
They wrestled for a bit, and at first it was Seto who had the upper hand. But while he was stronger, Mokuba was sneakier. He wiggled his fingers into the side of Seto's chest, and any semblance strength left his body in an instant.
"Do you give up yet?" Mokuba asked, sitting on his brother's stomach and tickling him relentlessly. "Do you?"
"Never!" Seto writhed and tried to shimmy away, but his brother's weight kept him firmly in place. His stomach was beginning to hurt from laughing, and he barely had barely had enough power left in his limbs to try and fight his brother off, let alone actually do it – but his headache and anger from before had entirely been forgotten.
"In that case, I can keep this up all night." Mokuba doubled his effort, grinning almost maniacally, and Seto knew him well enough to understand full that he meant it.
After yet again failing to push the boy off him, Seto sighed. "Okay, okay. I give! You win!"
"And-" Mokuba didn't let up. Not yet. "And I can have ice cream for dinner?"
"Alright, fine! Just—!"
As luck would have it, that was the very moment the door opened and Isono stepped into the room.
And what a sight he was greeted with – his barefoot boss and the man's little brother; laying on the ground, the younger tickling the usually composed man into absolute submission. And as if seeing Seto Kaiba wriggling and giggling like a toddler wasn't awkward enough, the moment that followed was ten times more so.
Seto and Mokuba both looked up at him, remembering that he'd been sent out on an errand nearly an hour ago. An uncomfortable silence fell over the room. Neither brother made an immediate effort to move – they just remained there; breathless, dishevelled, hair and clothing an absolute mess.
Until finally, Isono cleared his throat. "Excuse me. If that's all, I think I'll be heading home for the night."
"You do that," Seto answered as professionally as he could.
Isono seemed like he wanted to say something else to them, but instead just nodded and retreated from the room slowly, mumbling about how he wished this was the first time he'd walked in on something so childish.
As soon as the door shut behind him, the brothers burst into laughter once again.
"So!" Mokuba got to his feet, pulling Seto up with him. "Ice cream for dinner, then? You did promise."