So, based on the full title of Cherry Magic, I know it's based on that trope where if you're a virgin for 30 years, you become a wizard. And from my own recollection, I know one of them gets the ability to read minds, but is still so horrendously oblivious he can't understand the main interest is gay for him, and keeps thinking the love interest is straight. Unfortunately, one of KisaIta's best strengths is their communication, so this is a difficult AU to do for them fadsjdsll. I'll do my best interpretation of Suitable Arrangement by Ant_Bee to achieve this, since they've written one of the best cases of KisaIta miscommunication I've ever seen. Between the two of them, I think Itachi has the mind reading power, since he's more likely to overthink and not be used to interpreting people's more intimate/personal thoughts and could potentially be dense about it (is more likely to write those off or make excuses for certain thoughts to himself.) Meanwhile, it's very easy to interpret Kisame either way, as either having sexual experience, or being somewhere on the asexual spectrum and while he's not shy about sexuality or intimacy, he just hasn't had anyone catch his interest until Itachi. So I want to make Kisame Itachi-sexual and a 45-year old virgin with the ability to control water on a small scale and talk to sharks. Also, since I'm unlikely to make this an actual fic or anything anytime soon, I'll leave it to audience choice if Kisame is canon shark man Kisame, or Black/half-Black half-Japanese Kisame.

I think the premise will be just a little ridiculous, but the rest will be pretty grounded of like "I can maybe see this happening in real life, or at least suspend my disbelief and pretend this is a scenario that could happen IRL." I think Itachi's main job is being a corporate mercenary, where companies can hire him to work for rival companies and ruin their sales from the inside for a specified amount of time, or do other kinds of sabotage. I think he's been doing this since he was 22, and is just great at doing cold reads of people, and eventually he developed the perfect power to accompany this skill at 30. I think the Uchiha family tends to have kids when they're older to maximize the amount of time they have access to their powers, and they all tend to develop these genjutsu, mind manipulation-y powers like creating illusions, reading minds, copying skills and techniques, type of things. So a lot of them go into more high profile fields like lawyers, CEO, intelligence gathering, etc. So Itachi just being a salary man basically makes him kind of a black sheep in the family, but he's good at it, it makes a lot of money, and keeps Sasuke out of the typical Uchiha jobs as well so he can pursue a more artsy path in life, so why should he change. His most recent job is to ruin Seven Swords Seafood and Cookware. I think it's just funny if the Seven Swords in this AU sell knives and manage fisheries.

I'm going to base some of this on my favorite salarymen BL, Akuheki by iimo, because that's my strongest understanding of salarymen BL since it actually has the business stuff be a main plot point. But, basically, Kisame is Itachi's senpai in the company and shows him around, and Itachi discovers he's basically a 45 year old virgin who uses his water manipulation powers to pull neat tricks at the water cooler and make heating up instant ramen more fun by making shapes with the steam while he waits. Itachi is immediately like, "I need him carnally, but that would destroy my entire life's work." So to continue denying his feelings and the way that Kisame is flirting with him and is surprised by how much he likes Itachi, Itachi finds a woman co-worker from an affluent family who's interested in Kisame as well, but her family is particularly picky that she marries a man of status. So Itachi gets sidetracked on the side quest to turn Kisame into her family's ideal man by getting him promoted to section chief and all these other nitpicky requirements. Meanwhile Kisame's just... "wow, Itachi-san is really good at his job and likes me a lot, I'm excited to ask him out on a date to my favorite restaurant."

Most of the external tension and conflict is going to come from Itachi wanting to quit his job because he genuinely wants to be with Kisame. Eventually Sasuke encourages him to go for it, because when's the next Kisame going to come into his life? So Itachi eventually fakes his death and hides out in this remote village where his company will never find him, and sets up a nice house near the beach and a fishing boat for them to live at, and Kisame eventually finds him there.

I do think that Itachi has a friend at his company who vouches for him dying, and even if the company finds out that Itachi's still alive, the friend will confirm that he's no longer a virgin, and therefore no longer useful, or a threat to them, so leave him alone. I think Itachi finally getting rid of his power and embracing Kisame fully would be such a nice symbolic thing, and it's a pretense he hides behind, but they both know that it's truly Itachi choosing Kisame and wanting to do this with him.

Also, here's your bonus Isekai Office Worker headcanons:

Isekai Office Worker is about Kondou Seiichirou who stumbles on a young woman getting sucked into a portal. When he fails to pull her from the portal, they both get sucked into it and sent to a fantasy world, where Yua is a saint who will save the fantasy world from a curse called the "Miasma" while Seiichirou asks for work, and gets assigned to work for the accounting department, where he starts trying to make their lackadaisical staff into a functional accounting department that actually manages the books properly to make sure there's an emergency reserve fund for when the Miasma starts wrecking havoc on the world, but also because he can't live without working.

This world and premise is so fitting for a KisaIta AU to me, since Itachi being Seiichirou and Kisame being the super hot captain of the Knights Third Order who is a prodigy at magic and the blade is perfect. Honestly it could also go both ways where Kisame's a normal office worker who's found his only purpose in working could be similar to Kisame's dedication to Obito's promises of a new world, and ends up getting distracted by Itachi who he just jumps at every command Prodigy Knight Captain Itachi gives. But I think with Seiichirou giving Aresh some sass back whenever Aresh tries to care for Seiichirou is a more Itachi thing to do. Also, Itachi having Anime Wasting Disease from using the Mangekyou Sharingan in Naruto canon is a great parallel to Seiichirou's mana/magic sickness. On that note, I do prefer ItaKisa, where Itachi is the top, and there is a moment where the Isekai Office Worker protags speedrun getting into the relationship where Seiichirou nearly dies and Aresh has to save him using magical healing cock; I think it would be so peak for Itachi to be the top in that situation, especially with how that scene plays out in Isekai Office Worker. It's good both ways honestly, but just, small Itachi bridal carrying giant Kisame and being so gentle with Kisame is *chefs kiss*