Alright, so, I’ll start this off by saying I am honestly not an expert on Kakyoin, contrary to popular belief (I’d actually consider myself more of an expert on Jotaro’s character, if anything), but I’m going to do my best to give my views on Kakyoin’s character, as well as some canon evidence to support it, and hopefully it will help a bit.
If you want a great reference of how to write Kakyoin in fic, go read Sand, sand and more sand on AO3, because it’s honestly one of the best depictions of Kak I’ve ever read, and he’s quite close to canon.
Kakyoin is pretty snarky. He’s subtle about it, but he’s also kind of a shithead. He’s polite most of the time, but it seems to be more of a setting he defaults to when he doesn’t feel entirely comfortable around the people he’s with. We have quite a few quips from him as examples of this, such as him laughing at andd mocking Anne during the dark blue moon arc, and saying she couldn’t possibly be the stand user on board, and in the Geb and N'Doul fight where he orders Polnareff to attack the canteen because he “doesn’t want to”. He also at one point responds to Polnareff saying “this looks bad!” with, “well it most certainly isn’t good.”
He’s blunt, but this also means that he’s honest. He dislikes liars, and prefers that everything is set out before him clearly and plainly as opposed to someone that is clearly dancing around the subject.
He also seems like quite the know-it-all, and likes being right; and he’s probably the type to argue with someone even if he knows he’s wrong. He seems to genuinely enjoy teaching the crusaders about the culture of all the places they visit on their journey, and he has the ability to retain all of that information to recant to them, as well. It seems to be somewhat of an interest of his.
And then there’s this, of course…
The cherry thing is something that kind of bothers me in fandom and fic. Yes; Kakyoin says that cherries are his favourite fruit. Child Kakyoin has cherries on his shirt (keep in mind that the scene with child kakyoin is added in my DavidPro and is not technically canon). BUT, it doesn’t mean that he has to have everything cherry-related. It’s a seriously overused trait in fandom to the point that it just becomes annoying. Kak can have a coffee without it having to be cherry flavoured. Just remember that he canonically enjoys lots of different foods, and that he doesn’t need to exclusively eat cherries and cherry flavoured things. He probably likes to eat foods from all different cultures.
Video games: There is evidence to suggest that Kakyoin spends a LOT of time playing F-Mega, however, this doesn’t mean that his extreme knowledge of the tracks and mechanics applies to every video game in existence. He’s a teenager, with no friends in the 80’s, of course he’s going to spend time playing video games. But back in the 80s, people often only had one or two games, so it’s likely that he has simply replayed F-Mega a LOT, to the point of knowing it by heart. I know the levels of Mario 3 extremely well, simply because I played them over and over again as a kid. If you are fixated on a single game for extended periods of time (especially if it’s the only game you own), you are of course going to know the game well. Knowing a lot about a single game does not mean that he’s obsessed with video games, and does not necessarily mean that he’s a shut-in, and never goes outside.
Also keep in mind that he says that he’s “pretty good at video games”. He doesn’t claim to be great at them, and since we’ve already established that Kakyoin is quite blunt, it would be out of character to assume that he’s being humble here. He literally means that he’s just “pretty good” at them. No more, no less.
His real-world experience is vast, and it’s also mentioned that his parents take him many places on vacation. He’s been to a lot of places, and retains cultural knowledge. It’s not as if he’s read it in books: he’s actually been to these places before, and he mentions it frequently. This suggests that he gets out quite a bit, and also kind of suggests that maybe he isn’t quite the model student type in school.
Kakyoin doesn’t appear to be the honours student & straight A’s type. He doesn’t think twice about skipping out on his new school to travel to Egypt, and as I said before, his knowledge appears to come more from first-hand experience rather than school studies (and I bet he missed more than a few of his classes due to the trips that he and his parents took). He’s a know-it-all, but it doesn’t mean that he does well in school.
On the other hand, Jotaro IS a model student, despite his delinquent status. It’s more likely that Jotaro would be the one helping Kakyoin with his homework.
(He might disrespect his teachers, but he still gets good grades, and let’s not forget that he becomes a marine biologist later in life.)
Kakyoin’s profile also mentions that he “appears very effeminite”. This is another thing that is often misinterpreted. His appearence may be somewhat feminine, and he takes pride in how he looks, but his personality and mannerisms are not inherently feminine.
He hates being forced into submission, and this is the reason why he despises Dio so much. Dio took advantage of his vulnerability and the fact that Kak didn’t have any friends to use him as his pawn. He drew Kak in, made him feel wanted, needed, and then took control of his mind and body.
“He appears to be very effeminate. In reality, he despises submitting to people or sucking up to them.” - Taken directly from his canon personality description.
Another thing that people seem to miss is the fact that he’s extremely sadistic. He says himself that Heirophant “loves nothing more than to rip things to shreds” and that it might “drive him mad with joy”. He likes being in control of the situation, remember. He probably hates losing fights, as well (especially since he could be considered a weakling for losing).
Kakyoin also seems to like Baseball, judging by his profile naming a favourite team, and sumo, as we all know from his exchange with Jotaro.
One of the things that fandom does definitely get right, is Kakyoin being the mother hen of the group. He’s taken on the role of the responsible one, because Joseph is… far from being an adult. He’s strategic and thinks everything out logically, and so is the mature one of the group, especially after Avdol’s “death”. He appears to be content to follow Joseph, but when it’s needed, he steps up and becomes the leader in his place. This is seen when Jotaro, Joseph and Polnareff start physically fighting random men that they suspect are the one in the Wheel of Fortune car, to which he says that, “this is not a good idea,” and that it’s, “getting out of hand”. It’s also seen in the tower of grey fight where he mentions that it’s better that he fights on the plane, because he’s the least destructive of the bunch (even though he’s capable of blasting holes into clock towers, apparently his emerald splash isn’t destructive; okay Kak…).
He’s also fiercely protective of his friends, and extremely loyal as well. Kakyoin isn’t the type to abandon his friends in any circumstance.
He’s a CASANOVA. While Jotaro draws more unwanted attention from girls due to his bad boy façade, Kakyoin is slick and smooth with them, so much so that they notice him more over Jotaro. He’s quick to diffuse the situation when Jotaro pushes the girls aside (again, in the tower of grey arc), and it’s just… yes.
Just look at this. You can bet your ass he’s not the type to blush and stutter as he’s confessing. Straight up grabbing the girl and apologizing for Jotaro. Smooth as butter.
Here are some other scenes that might be able to explain his character a bit better as well:
Mouthing off to Joseph- Jotaro approves.
This line is wonderful. (Again, to Joseph? It’s almost like they have this kind of rivalry going on, haha)
Some really good insight to his character and motivations (And one of my favourite Jotakak moments).
The anime kind of makes this out to be a sort of “Kakyoin mocking Polnareff” scene, but in the manga he seems like he’s just stating what he heard. Pretty matter-of-fact about the whole situation.
I believe that this is the first moment that Kakyoin really realizes that he and any of his companions can die at any moment. Avdol has been shot, and he’s in complete shock. This is a normal teenager that’s now painfully aware of the danger he’s putting himself in to help out Jotaro and Joseph. Sure, he realized that he would be involved in fights, and a little blood would be shed for the greater good, but I don’t think he had realized up to this point that he might actually die.
And here’s Kakyoin’s character bio.
It’s also notable that he didn’t tell his parents where he was going prior to leaving. This doesn’t necessarily mean that he’s in bad standing with his parents (especially since his dying thoughts were of them), and could possibly be because he didn’t want to worry them, or something of the sort, but the fact remains that he didn’t tell them beforehand. Take from this what you will.
So yeah, this is what I get from Kakyoin. He’s kind, loyal to a fault, and deeply in love with Jotaro– and he’s a pretty complex character to write. Don’t feel like you need to take all of this into account, because it’s hard to keep his entire character intact with fanfiction. A lot of his personality comes across in facial expressions, so it’s sometimes difficult to translate that into non-visual media. Just refer back to canon if you aren’t sure of something, and you should be fine. Good luck!