definitely the latter... if he actually had a partner to act it out on him he'd ironically be more confident in his gender and have less self image issues
but in his eyes, he thinks hes a "freak" or "fake" for having such a desire thats opposite of his ideals(being respected as a man) despite it only being a fetish
there are also other characters that i hc trans, so being in an environment with others like him just makes tatsumi more guilty and feel disrespectful
his want to conform to typical masculinity is killing him its crazy
i havent thought of anyone who shares the same fetish or would indulge it, so he will have to suffer alone a little more...

*This is prefacing that Tatsumi is transmasc

Struggles with body image and dysphoria as an older trans person, due to not having the proper resources and growing up in a strict religious family.
This leads into a frustrating relationship with sex- example:
-He wishes to be the typical masculine top, but gets insecure for being not "man enough". Tatsumi feels more comfortable receiving, but again, gets gender insecurity. Strap-ons make him feel worse, and only wishes he had working dick in the first place.
However, he has a very passive nature and lacks legitimate sexual experiences with others, so he can attempt to be a service top and try other equivalent roles if his partner asks in order to please them.

Things about his body:
-I draw him with top scars but in my head he has only gone through HRT, and is no op(fear of committing to surgery and the thought of surgeries in general). He has around a B-cup and binds often. Wears baggy clothes often too.
-A sprinkling of moles throughout his body. Prominent ones are on his neck, tummy, and inner thigh.
-Belly fat.... belly fat.......
-His lower back is his erogenous zone. It's difficult to get massages because of this.
-Softer hands, softer feet.

Fetishes and habits hcs:
-Spanking. Grown from childhood trauma, probably.
-Makes no noises when masturbating. See above.
-Dislikes being drooled or spat on. Immediate turnoff.
-Enjoys spider touches.
-Really likes sensory deprivation and overstimulation.
-Has a fetish for being misgendered and shamed for gender insecurity. This was due to Reimei. The thought of his partners or others thinking he's weird for wanting this acted out on himself makes him too embarrassed to actually use it as a cope mech.
-Tries to hold hands during sex.
-Tends to close his legs together instinctively. See the first point.
-Doesn't object to the use of religion during sex, such as wearing certain clothing or roleplaying, but definitely overthinks about the morality of it after.

hope this is all concise enough to read through... would love to talk more about certain scenarios but this is what i could think of on the top of my head

Ignihyde as a dorm isnt my interest HOWEVER the dynamic of shroudcest specifically is super interesting, heartbreaking, and opens the gates for everything gross- i very much enjoy it even if they arent my focus :) (im a jack and jamil oshi)
I do especially like Ortho taking the lead despite idia being strange and modifying his brother's body- making a body for his dead brother at all- to be fit for him and only him. I think dom Ortho comes from half preprogramming and half putting Idia's needs above all else, ignoring typical morals because of everything that's occured in the past and loving his brother unusually but also... he IS just a bot now. TLDR Idia does not want to control Ortho in the first place, just needs his exsistence by his side, and Ortho unintentionally takes advantage of that by setting up nasty cope sex or whatevers equivalent
Sorry if my thoughts arent as sexually charged, i draw filth and porn but mouth speaks slight introspection into character relationships ^^

Idfk why there's barely any ES artists that indulge in oldmanifying the cast when they are so ripe for the taking.... shaking my fist
And yes, Himeru is confirmed not 18-ish like the OG Himeru and is actually older, which is extremely funny and frustrating because happyele will never jump on the idea of old people fumbling to fit in as idols and amongst MUCH younger juniors. I'm with you with denying canon here, I may read the stories but they can benefit from age changes in my rotten little head
The characters I see as much older(at least most of the time) are Tatsumi, Mayoi, Himeru, Madara, and almost all of Oddballs. Tatsumi is definitely in his 30s, I didn't play for a long time since ES! so when I found out about Alkaloid I kept staring at Tatsumi like... did happyele just put a random old guy in there..? thats religious and is terrible at technology... and has health issues... you cant tell me he was never not supposed to be some middle aged guy hes so moe... I dont have set ages for the others listed but they're all at least in their 30s or about to hit 30
-but ah, I don't think the fandom very much likes old men suffering so I can only talk about this so much </3