Hi lost, I'm not sure either but seems like this is a Chanto Suki tte Ieru Ko Musou (harem cast) mixed in with Osoraku Kanojo wa Ore no Aniki wo Neratteru (MC).
Edit: But with an arguably slower pacing than both of them
I would argue that its just a far worse version of Chanto, where someone tried to copy it, but wanted to change enough to not be outright identical, but everything they changed made it worse than Chanto. MC is lame, girls are weird walking landmines. The openly honest girl with her desires is instead for now an enigma who could be either just a weird past friend or an lesbian using MC to get the girls herself, or a mastermind having fun with other people feelings. Most of those is lame compared to Chanto. The main girls in Chanto were just your typical shy/tsunderes/not honest with their feelings, but it worked with the contrasting new girl who is open and honest with herself and her feelings and her pursuit of MC, who himself is your normal cringy at times (mostly when trying to flirt) dude. While all characters in this one are overthinking everything weirdos, dude rizzed them up by mistake aka he didn't even knew he did, girls thus falsely believed he is into them, while the new girl is just thrown it to "mix" shit up.
I am reading this still cause the "new" girl seems cute visually (better than the main trio) and I am curious what kinda plot twist they will come with for her. Personally a tame "she knew him ages ago" and just wants all his first for herself cause she is into him would work best for me, otherwise make her as crazy/weirdo/alien out of this planet as could be - and I don't think lesbo or mastermind trying to use him for fun/stealing girl would be that - something even crazier would be needed. Apart from that its not really that good of a story thus far. Mind you Chanto isn't some genius gem either, for one none of the main cast of trio girls and new one interest me visually/character wise - the commenting and finding it all funny blond friend of the tsundere from the club side girl seems best thus far

and with how much screen time she has, I wouldn't be shocked if she joins the harem as a candidate at some point.