this is insanely romantic. i'm sold. like, i'm already a sucker for class S-inspired stories (marimite, anyone?)
I always thought Marimite is a weird one. Yes, it has all the surface elements of a Class S story (sisterly bonds, rosaries and the like), but almost none of the elements that make Class S so distinctive. Most classic Class S stories have a heart of love, longing and outright lust, and Marimite has almost none of that. It's mostly the antics of high school girls who like role-playing Class S tropes, but there's no there there, if you know what I mean.
The few times Marimite seems to be going into a more romantic direction it gets treated as if it's something to be avoided, such as Sei's backstory. It's also telling that by the end the only official couples are heterosexual ones.
Strawberry Panic, for all its silliness, seems to get al least the romantic and lustful part of Class S right.
fwiw this is only really true of the strawberry panic anime. i'm a fan of the light novels specifically. in there, yaya is described as "a bonafide lesbian" like it's a dirty, controversial word. that unlike the other girls, her love is explicitly sexual (and it ties this into her issues at home with her father etc). and that combined with her assaulting/raping hikari... it's definitely not positive about the lustful side.
(for anyone wondering why i prefer the LNs, they're much bigger on the inter-school politics and competitive drama, and shizuma/nagisa has much tastier chemistry.)
also idk if sei's backstory was framed as "bad"? granted i haven't read the marimite LNs, but in the anime, i thought the delicate treatment was because of how deeply personal and sensitive it was. sei (my favorite character, incidentally) was deliberately snuffing out her own vulnerability after everything that happened. considering how badly her heart was broken, i can't blame her.
regardless, i agree that this manga is very deliberate and faithful toward its class S inspiration. latest chapter surprised me, but kasumi's issues have been quietly building up to this for a while, so i think it only feels a little jarring because we're reading chapters as they come out vs binging. the seeds were definitely planted early on.