Appearance
General
In most games, Akihiko is depicted as a thin teenager of approximately average height. In most games, he's the second tallest male member of SEES (after Shinjiro). He has greyish white hair, and his eyes are usually grey, though in the anime they drift to a more grey-brown.
The greatest mystery of this website is, of course why he wears a bandage above his left eye from at least the age of 17 until the age of 20. Embarrassing facial scar? Witch's curse? To keep his brains from leaking out? You decide. Flashbacks to childhood show the bandage on his nose instead. Food for thought, dear readers.
Persona 3
Uniform
Winter
Akihiko wears an approximation of the Gekkoukan School Uniform for most of the game (I would have been sent home if I had tried to wear my school uniform like any member of SEES, but I digress).
For the upper body, the base layer is a long-sleeved white Oxford shirt buttoned up fully with a black ribbon tie. The shirt sleeves have a garter on them which he generally slaps his SEES armband over without considering how convenient it would be to use them to hold said armband on. The armband is only worn when exploring Tartarus.
He does not wear the uniform jacket, though is often depicted carrying it in official art and at times in game. Instead of the jacket he wears a red button-up sweater vest which has a gold lowercase 'b' on the left side of the chest.
I really did my best to find an official answer for what the 'b' on his sweater vest is but came up short. As far as I can tell, the best answers are that it's the branding on the vest or an indication that he's captain of the 'b'oxing team. Personally, the redditor who said it stands for 'baby baby baby baby' cracked me up so let's give them 'b'onus points.
On the lower body, he wears black uniform slacks with a brown belt - though when fighting during the Dark Hour it is often covered by a white gun belt where he holsters his evoker.
The colour and style of shoes can vary between different games and sources. Always some sort of dress shoe, in the base game they are black-to-dark brown, usually plain though some official art decided to go for some funky wing-tips.
And of course, Akihiko nearly always wears thin black leather gloves. Usually they fully cover his hands but in the anime there are small cutouts on the back.
Summer
Same as winter, though with a short sleeved Oxford shirt that doesn't have a sleeve garter. He never wears the summer uniform with a SEES armband.Casual
Winter
When not in uniform, Akihiko's winter attire consists of a white jacket that reaches down to his hips over a black button up shirt. Over that, he wears a lightly knotted red knit scarf. His pants are a slightly darker grey with a brown belt and brown shoes. SummerHis summer casual attire is a red v-neck t-shirt with slightly lighter red vertical lines running down it. His pants are a lighter grey, verging on white, and his shoes are brown.
Yakushima
The Yakushima trip is, of course, where the man becomes the legend. On top, he wears a white t-shit in most scenes, though he does go shirtless in a few scenes. In Reload, the shirt has S.O.S. printed on it in grey. On the bottom, our bough naught but a purpley-blue Speedo. He shows zero embarrassment with this decision, pointing out that competitive swimmers generally dress as such. Though this is, rightly, played for laughs I do enjoy this really distinct method of characterizing him and lets us truly appreciate how delightfully weird this guy is.
School Trip
On the Kyoto school trip, like all the other students Akihiko wears a purple haori over a white kimono with grey circles on it.
Episode AIGIS/The Answer
During the flashback to a younger Akihiko we see him wearing a red crew neck t-shirt under a white Oxford shirt with the first button undone.
Persona 3 Reload Changes
Persona 3 Reload only changes some minor details in Akihiko's regular looks. Specifically the mysterious 'b' while present in dialogue bubbles vanishes when he uses his finishing touch in tartarus and in general his shoes are a much lighter shade of brown.
SEES Uniform
In Persona 3 Reload all of the members of SEES are given special uniforms for Tartarus exploration. In Akihiko's case he primarily wears his regular school uniform however he replaces his Persona 3 gun belt for a black shoulder holster leaving his Evoker under his armpit instead of his hip. Instead of keeping his evoker on his hip he keeps a small pouch on his belt on the back. His sleeves are rolled up and instead of the basic SEES armband wears a shoulder guard with the number '01' on it (He's the first member of SEES after Mitsuru, number '00').
His gloves are a more standard boxing affair. They are fingerless and much more padded than the leather gloves of yesteryear.
Cooking
At various times in Reload you cook with your companions. When in the kitchen with Akihiko he wears a red apron over a white shirt with brown pants.
Movies
Gym Attire
During gym montages in the Persona 3 movies Akihiko wears a white t-shirt with grey shorts.
Persona 4 Arena/Ultimax
General
Shirts are for casuals. Capes are not.
P4AU is set two years after Akihiko has graduated from Gekkoukan High and is 20 years old. Yakushima of course proved to us that Akihiko is a big 'substance over style' kind of guy when it comes to working out which P4A doubles down on. Akihiko tells us himself that he picked his style to facilitate training (no capes!) Silhouettes are especially important in fighting games to quickly work out hurt/hitboxes and I assume bulking him up helped to differentiate him from the rest of the anime children in the cast.
To that end, he wears a red cape that reaches to his knees, and billowy brown pants tucked into red lace up boots. He wears a belt with a combat knife, water bottle and pouch attached to it. Despite not needing an Evoker in the TV world he wears his in a shoulder holster under his left arm. His boxing gloves are also red.
Physically, he has also made some changes. finally all that protein seems to be doing something for he's distinctly broader in the chest. Deciding Junpei's goatee failure should be an inspiration he is also attempting to rock one. His bangs are cut much shorter and he's covered with scars but don't worry fans, because his bandage is still there. So how some way. There is also a bonus leg bandage.
Usually the hood is down but when he is attempting to be mysterious he keeps it up. Also during mysterious scenes he carries a brown satchel.
Suit
For some reason Akihiko opts for his Kazuma Kiryu best with a white suit, though he wears a black shirt underneath instead of an extremely extra shade of purple. As far as I know you never see his shoes when he wears this outfit, but when I replay the story mode I'll keep an eye out for it.
Persona -trinity soul-
As I had yet to watch -trinity soul- I can't fill this section out yet. Stay tuned for when I get around to watching the anime though!