beware, for you have entered... THE SEXY ZONE!!!! here is where i'll post my NSFW headcanons about daiken, featuring kinks galore!!
daiken or kensuke... ah, the age-old question. as you can see by the name of the site, i'm daiken-leaning (plus it just sounds better as a ship name), but i'm really not very invested in who tops or bottoms in my ships. daisuke is more of the instigator between the two, seeing as he was the one who went after ken in the first place, and ken definitely exhibits more Bottom Behavior, so daiken ends up being the default. but i think they're pretty evenly matched in all aspects of their lives and the bedroom would be no different. ken has a mischievous streak and i can easily see him becoming a real tease when he wants something, and i see daisuke as primarily a "service top" in that he's more interested in giving ken pleasure than receiving it himself. and they were both subs???
it is my humble headcanon that the dark seed accelerated some aspects of ken's physical and mental development -- making him smarter, more athletic, and TALLER(that dark seed growth hormone is real) -- but stunted his sexual development, since it was of no use to it. this results in ken being far more sexually repressed than daisuke, who, let's face it, has probably been jerking off since the first time he got a boner. i think ken would know more about sexuality from just a scientific standpoint, but daisuke would have more hands-on experience. this works perfectly with the headcanon that ken is more aware of the Gay and panicking over it while the sexually-charged daisuke is just going with the flow and making all the moves on him without realizing it.
speaking of growth... it is my very steadfast belief that ken's dick is bigger than daisuke's. in fact, daisuke's dick is pretty small for his age, matching his shorter-than-average stature. ken's, by contrast, is longer and thinner than daisuke's, just like the rest of him. at first daisuke is sensitive about his size and worries he won't be impressive enough for ken, but ken makes it very clear that he is super into daisuke, no matter how big or small any part of him is. i'm incredibly fond of this headcanon and work it into all my art and fics, even going so far as to write an entire fic just about it.
since i'm a big cardiophile (a heartbeat fetishist, explained in more detail at my history page), it's hard not to imagine daisuke and ken being cardiophiles too, the degree of which differing from fic to fic. i like to think that daisuke, who made all the grand speeches about how amazing it felt to have ken's heart beating alongside his own, is so obsessed with the feeling because of his latent cardiophilia, which he realizes when he ends touching himself to the memory of ken's heartbeat. (that specific scenario is one of my favorite for daisuke's sexual awakening haha.) but sometimes it's also fun to imagine that daisuke is truly clueless and ken is the one agonizing over all the heart shit he says to him, unable to handle him talking about it all the time because it's way too horny for him (much like myself). either way, i think they definitely incorporate this heartbeat connection into everything they do, whether its feeling out each others' heartbeats while making out or just cuddling and listening to them, they're a big source of intimacy for them.
furthermore, i think jogress itself is a big kink for the two of them, and definitely their sexual awakening, even if they don't realize it immediately. after all, jogress is sex. and to have sex while jogressed, well, that would just be the ultimate in ultimate, wouldn't it?
it's highly likely that with all of his guilt and angst, ken would be into some masochistic and possibly humiliating stuff. it would definitely be hard to get daisuke to do anything resembling "punishing" him, but maybe with some education in BDSM, they could come up with a healthy way to work through ken's trauma.
weight gain (and the stuffing that leads to it) is another one of my biggest kinks that i have applied frequently to daiken, specifically daisuke. like i mentioned on the regular headcanons page, i headcanon that daisuke starts getting chubby once he starts preparing for his future as a ramen chef. he's always loved to eat, but i think that it's totally likely that when he ups his ramen intake in the name of "research" he starts putting on some pounds, resulting first in a cute gut and then some overall pudge by the time he's a full-fledged apprentice. another way i like to imagine him gaining weight is through trying to put some meat on ken's bones by inviting him out a lot and cooking him an excess of food, a plan which backfires when ken barely grows and he does instead. no matter the source of his gains, it's imperative that ken is extremely into daisuke's new look, with both of them realizing they're super into feederism as a kink!