Head cannon please if Munakata and Fushimi had met many years ago as kids before they had to part and didn't remember each other at first
Maybe something similar to the First Contact comic in LSW except tiny Munakata and tiny Fushimi actually spoke to each other a bit. Oh, since Fushimi lives in that big house imagine Kisa hires Munakata’s family to do the landscaping and maybe Munakata gets to tag along because there’s no babysitter, like his mother is away visiting her parents and Taishi is at like summer camp and the person who was supposed to watch little Munakata fell sick so Munakata’s dad has no choice but to bring Munakata along. He doesn’t anticipate there being any issue as Munakata is an oddly well-behaved child and the worst Munakata’s dad figures could happen is Munakata wanders like into the study of the house they’re working on and starts reading all the encyclopedias or something (and even then he would be sure not to dog ear any of the pages and would place the books back perfectly in alphabetical order by author and latest edition number). When they get to the house Kisa and Niki and aren’t home but the housekeeper is, however she’s just about to leave to go home. She tells Munakata’s dad that he’s free to come inside if he needs a drink or anything, as the family never locks the doors and that Munakata’s dad probably won’t see anyone until he’s done if not later, Kisa will be working late and Niki’s who knows where. Munakata’s dad was paid in advance so he doesn’t mind but he finds it a bit odd that Kisa would pay him and all but not even bother to be home to look at the final product.
So Munakata’s dad starts working on the bushes and he tells Munakata to just sit and watch, Munakata’s observing when he spots a small face in the window. He points it out to his dad who is surprised to see there’s a child in the house, one even younger than his and with no supervision. Somewhat concerned, he suggests that Munakata babysit little Saruhiko while Munakata’s dad finishes the work, figuring that Munakata’s responsible enough and this will give Munakata something to do while his dad works. Munakata goes inside and finds Fushimi on the couch playing a video game. Munakata sits next to him and asks what he’s doing here all alone, Fushimi just shrugs and mutters that he’s always alone. Little Munakata finds this worrying but asks why don’t they go outside and play, Fushimi just shrugs again and says he doesn’t usually go outside. Munakata suggest maybe working on a puzzle then, Fushimi says there’s one in an unopened box in his room if Munakata wants to play with it but Fushimi’s fine this way, not seeing any point in getting attached to this strange kid. Munakata goes to get the puzzle but then he brings it back down and starts working on it in the middle of the room, going slowly because he can see Fushimi watching him. Soon Fushimi’s obviously not even playing the video game anymore and Munakata finally asks if Fushimi wants to help him. Fushimi mumbles that he doesn’t see the point in doing a puzzle, won’t it just get broken apart eventually. Munakata thinks for a moment and then smiles brilliantly, saying that in such a case that simply means they’ll have to put it back together again. Fushimi’s eyes widen a little and he ends up on the floor with Munakata working on the puzzle together.
An hour or two later Munakata’s dad comes to collect his kid, Fushimi’s a little crestfallen that Munakata’s leaving but then again it’s not like he expected Munakata to be here long anyway. Munakata says he will certainly be back next time, after all they never finished the puzzle. Fushimi looks almost hopeful as he nods, and maybe after Munakata leaves Fushimi carefully gathers up what was complete of the puzzle and transports it back to his room, hiding it on his desk under things in the hopes that they can eventually start from where they left off. Unfortunately one of Kisa’s clients has like a son who does landscaping and Kisa just has him do theirs after that, trying to curry favor with her client, and so poor Fushimi never gets to see his friend again and soon he’s almost even forgotten that old half finished puzzle (one day when Yata’s over he finds it and asks why Saruhiko has half a puzzle on his desk, Fushimi’s eyes get far away for a moment before he shrugs and says no reason, sweeping it off the desk and into the garbage bin).
So then flash forward and Fushimi joins Scepter 4 and at first neither he nor Munakata remember each other. But every time Fushimi sees Munakata putting together a puzzle there’s something oddly familiar in it that he just can’t quite place. He shrugs it off, thinking it’s just his brain making things up. Munakata probably remembers first, like he really never forgot that little lonely kid and the puzzle they never got to finish and when he first sees Fushimi he thinks that Fushimi is very like that child. Then maybe one day the two of them are out on some kind of patrol and they pass by Fushimi’s old neighborhood, Fushimi mentions that he used to live here and Munakata gives him a keen look, now probably quite sure who Fushimi is. A couple days later he invites Fushimi into his office and there on the floor is a new puzzle but not one of his usual ones – this is a child’s puzzle, and only half finished. Fushimi stares for a long moment as Munakata smiles and holds out a hand to him, saying it took some time but he would indeed like to finish this puzzle with Fushimi, as promised.