Clothing/Appearance:
Allegory of Whatever describes him (and I believe this is a direct quote from Japanese source material) as "A tall, handsome young man. He looks very mature." He's 181 cm tall (so he just barely misses hitting six feet), and weighs 68 kg (150 pounds), which I guess puts him at being a fairly typical anime-esque noodle boy. why does my character have a more girlish figure than I do edit; Although now that I've looked at other people's stats, this must be reasonably well-built for Personaverse, because he weighs more than Kanji. wtffffff
He has brown hair and eyes. His hair...frankly looks kind of ridiculous in Kaneko's art, and my mental image of him does actually fall closer to how
doujinshi artists like to draw him, because they make his hair not suck. (And considering that in Innocent Sin, his entire school pretty much idolizes him, I think it is kind of important that he does not look completely idiotic, okay.)
Before canon updating, he had a scar from a knife wound on the right side of his back. Although he's in no way self-conscious about that, he also isn't prone to randomly wandering around shirtless, so I imagine very few characters would've had the chance to see it anyway. Since canon-updating, that scar has disappeared (or to be more accurate, never happened...to this body, anyway), and he's picked up something else instead:
the weird black mark. He does his best to cover this, but since it reaches his hand, there's only so much long sleeves can do. There's a strange design in the middle of it; Nyarlathotep basically left it there as a way of saying "lol, Crawling Chaos was here" (why tag buildings when you can leave graffiti on the bodies of your enemies?), and as such, it probably gives off some bad vibes to the psychically sensitive.
In general, you can safely assume that he's wearing the Seven Sisters High School uniform unless otherwise noted. Now that he's canon updated, he presumably does have that stupid red jumpsuit hanging in his closet somewhere, but he's trying to fake out the IS cast and pretend that absolutely nothing has happened, so he changed back to his old clothes at the first opportunity. Tatsuya...doesn't really care much about fashion, so wearing his school uniform also saves him the trouble of figuring out a better wardrobe. (My headcanon for this is that he doesn't care about fashion because his older brother does care so much about it; Katsuya is always seen in designer suits, and Tatsuya has gone to great lengths, both consciously and subconsciously, to distance himself from his family as much as possible. If his brother cares about fashion, he's going to avoid ever giving a damn about it himself.)
Habits/Mannerisms/Body Language:
Tatsuya's posture hits kind of a middle ground. He definitely doesn't have that great of posture; he's an apathetic kind of guy and he doesn't care enough to hold himself up straight. But at the same time, he does still have a definite presence. He's relaxed, probably a little slouchy, but not too much so -- enough to give that kind of "I'm too cool to care what you think" vibe, but not enough to come across as a complete slob. (Mind, I'm not saying he actually is cool. He is, in fact, a tremendous dork with a lifetime pass for free rides on the failboat. However, his classmates in canon all seem to think he's the coolest thing ever, so he can apparently fake it reasonably well, at least until you start talking to him.)
His body language is fairly closed -- hands in pockets, and it's obvious enough from the way he carries himself that he doesn't welcome invasions of his personal space. Although his default expression is pretty blank, he is capable of emoting pretty strongly if you know how to get to him (although I find his EP expressions seem a little more restrained than his IS ones, personally).
He is always always always carrying an engraved silver lighter -- it originally belonged to Jun's father, who gave it to Jun when he stopped smoking, and Jun gave it to Tatsuya when they were children. The engraving says, according to the Japanese script, "Being the most important can't be seen in the eyes." However, I am going to assume that the Engrishy fail is not actually supposed to be there, as amusing as it is, and therefore the inscription properly reads "The most important things can't be seen with the eyes." (Yes, it's a quote from The Little Prince.) Whatever Tatsuya is doing, he's probably flicking the cap on and off that lighter periodically. It's such a constant habit that if I noted every single time it happened, I'd want to stab myself. I do mention it occasionally, but for the most part, you can just assume he's doing it without me saying so.
Editing in some stuff about his speech here, since it didn't occur to me until I saw someone else put it in theirs -- his seiyuu is Koyasu Takehito, so his voice is pretty low. There's not a terrible amount of expression in his tone, either. He uses very casual 100% male speech patterns in the original Japanese, although idk how that would come across otherwise (does camp just...dub us all over?).
He also tends to keep kind of a safe distance in how he addresses people -- unless he considers you pretty close to him, he will be addressing you by your last name only. He's not very likely to use an honorific with that, because his social skills are pathetic and he doesn't care that he's being rude. The only real exception I can think of here is if you've only told him your first name, in which case he doesn't really have a choice but to use it. Even if you tell him to use your first name, he likely won't until he's pretty comfortable with you; thus far in camp, the only people on a first name basis are his canonmates (save Eriko, who he doesn't get much interaction with in canon), Yousuke, and Souji. (And he'll still occasionally revert to calling Yousuke by his surname if he thinks Yousuke's being a douche.)
Current Residence(s):
SEES Dorm, room #302.
Typical Daily Routine:
He likes sleeping in if he can get away with it, so he'll often get a late start. He doesn't skip meals, so extenuating circumstances aside (i.e. Tuesday), he will make it into the mess hall for every meal.
Aside from that, though, I don't think he really has a set routine so much as he hangs around, and sometimes gets dragged into things by the other Masquerade kids or by anyone else he knows. His tremendous apathy is constantly at work here; he just doesn't really have an opinion on "HEY TATSUYA WHAT SHOULD WE DO" most of the time, so if one of his friends comes to him and wants him to do something, he'll probably just shrug and go with it.
He does have a little more focus since his canon update, however, and will be taking some time to go train by himself every day without fail. Probably this is around early afternoon, and he takes at least a few hours; if there's nothing in particular going on and nobody tops him into doing something, maybe more.
Favorite Haunts:
SEES Dorm and the mess hall. Prior to the canon update, he would very frequently be found hanging around with Jun in the dorms, but he's keeping his distance from his cast a bit now. (Though at the same time, he's trying to avoid looking like he's keeping his distance, so he's around them, perhaps a bit less, and with a lot more awkward.)
Does he make his own bed?:
No. He just leaves the covers messy. Why bother when he's just going to mess it up again in twelve hours anyway?