i don't participate in any sort of svsss fandom stuff so my apologies if this has been said already but a HUGE part of the humor of that book comes from how it parodies typical isekai harem tropes and not just in the way you might think. there's the typical "wow so cheaply derived porn trope" humor but part of the humor is also in that despite LBH being the original protag, the book SVSSS itself features SQQ as the protagonist.....
ppl like to joke about SQQ's "harem" but the humor of the harem isn't just in that he has one at all (when normally that would be LBH's role), it's how every "member" of that harem fulfills a typical isekai harem role in an inverted way!!!!!!
most obvious example is LBH. he's an inversion in that he's originally intended to be an all-powerful demon king who's a housewife in SVSSS, but (imo) the humor in his "role" is that he's supposed to fulfill the trope of the young abused battle-hardened "demon" girl who longs for peace and housewifery and latches onto the older man who showed him kindness -- except instead of being a moe anime girl, he's an all-powerful protagonist-style power insert hero. so, not so much an inversion of "this demon king is actually a housewife??" and moreso "this housewife is actually a male demon king" (which might not sound like much of a difference at all, but it's moreso about how the MEN fulfill harem girl tropes and not the other way around.)
another example is YGY - set up as a "big brother" figure and clearly has history with SQQ. he's meant to fulfill the trope of the clingy "older sister" childhood friend who promises marriage to the protagonist and has clear history w/him but is insecure about his role because he's not as "appealing" as the other options. his humor as a "romance option" comes from 1. him being a man (you might notice this is the case for a lot of these LOL) and 2. actually, in fact, being immensely powerful - it's another inversion of the trope of the physically weak "starter" harem girl who agonizes over being unable to do more for her beloved childhood friend in their journey.
my favorite example: LQG is the most obvious "tsundere tomboy" trope ever. physically powerful, out of touch with her emotions, gets flustered and aggressive with her crush, focuses on getting stronger above all else yet somehow extraordinarily beautiful -- all of these are extremely obvious tropes assigned to this "tsundere tomboy" trope, with the humor lying in the contrast of LQG actually being a man. the succubus extra is hilarious not just because of the awkward situation and their reactions, but because it's an EXACT setup of an extremely common scene in isekai harem novels. the cold tsundere beauty gets affected by succubi, doesn't know what to do, goes to the protagonist for help - it's the exact kind of situation that would have the protagonist pushing her down and saying lines like "you shouldn't act like this - i'm a man too, don't you know?" and making her aware that she's a woman and "in danger" around him. it's funny because LQG is very much a man, and indeed SVSSS parodies this directly by having SQQ tell LQG that he's a man too, he'll understand if he needs to jerk off! no worries!
even ZZL falls into the trope of the typical beast-kin girl who's saved by the protagonist and falls into his harem, subverted by his loyalty to someone ELSE besides SQQ and nonchalance as he does it.
it's the main draw of the humor of the novel for me and i surprisingly feel like not enough people talk about just how much SVSSS really leans into being a parody of a harem-collecting isekai....
and if you're curious about my credentials for making this post: if you name a shitty isekai novel, i've almost definitely already read it all. i read too many midsekais. it's like an addiction.
