It's wildly exaggerated by insecure people. The two girls just kiss once and that's all that happens. Considering all the cheating Leon does on them, that's nothing.
The author of both series tends to change endings in between web novels and light novels, also, the light novel/manga version of Marie Route is quite expanded compared to the web novel.
And the 'Sister/Fiancee' thing is because right after where the manga adaptation stopped, Leon pops the question.
eh the manga adaptation stops there? gayyyy.
Also... Olivia and Angelica don't just kiss... they fuck, leon finds them and watches. That's straight up hard NTR bruv.
Now I don't know if that was from LN or WN, I just want to know if the manga story is different XD
Like this is what a reader told me:
"Now about Olivia and Angelica in the main route (Mubuseka) yes they cucked Leon. Confessed to each other then kissed and had s*x. Leon found them, hid and saw the whole thing. Then decided to take the L and leave.
Many things happened after with Leon distancing himself from them not to be a nuisance.
But author said "wait a minute this will make my dear Olivia less relevant in the story gotta make her a harem member somehow".
So Olivia and Angelica decided to confess everything to mr. Cuck-eon then he admitted he didn't want to be a third wheel but they said "let's be your girlfriends but keep our lesbian relationship" he said "okay". So technically they are part of the harem but also f*ck at Leon's back like a good cuck he is.🥴"
Which is more than a kiss. To double check I searched reddit, and it may just be WN where in LN they just sleep together (like literally sleep), since Luxion mentioned that, doesn't go into detail of anything else... but if they "love" eachother and sleep together often... do the math.
Leon in WN and read between the lines LN is the last to get close to them, and the last to touch them... and when I say last I mean LAAASSSSSSSSSSSTTTTTTTTTTT, takes ages for anything to happen with him, dudes proper third wheel.
And reading posts from readers on reddit.. yeah this is more than "just a kiss":
"in Leons case, everything happened behind his back. They stole each others first kisses, sleeping together naked etc that at some point you ask yourself do they even love him and leon gradually became a 3rd Wheeler"
Them doing shit together while leon is third wheeling... ain't really harem at all... that's just yuri with a guy friend to tag along :|
Dude still got cucked either way tho. Sure it only falls into the BSS category not "technically NTR" but still... BSS is shit if it's supposed to be harem XD
Again this is from readers, no idea if manga kept it or not, that's what I want to know
edit: Anoseka is def better, author should just ditch Mobseka and do that one instead, with a alt version that goes harem to do harem, since the foreshadowing of olivia and Ang is also in Anoseka to a degree anyway, and builds a lot more naturally too in a odd way.