Not gonna lie I don’t understand what if wrong with kokoro what makes her a red flag? Can someone explain it to me please I’m terrible with red flags
To start with, the backstory revealed that Kokoro's basically been obsessed with getting closer to Kurumi since they first met. Even when Kurumi's other friends realized she'd changed and had issues at home, Kokoro was in complete denial of those things. Kokoro can't accept Kurumi as anything less than perfect, just like Kurumi's mother. Kokoro nearly has a meltdown anytime something challenges her idealized version of Kurumi or their relationship. That's why Kokoro's first assumption when she saw the shoplifting video was to accuse it of being someone else's fault.
It's ironic Kokoro told Kurumi to open up about her problems, yet when what Kurumi had to tell her was that she didn't like her and she wasn't the person Kokoro thought she was, Kokoro told her to quit talking. Kokoro's reassurances are hollow. And to say she wasn't asking anything of Kurumi only to essentially guilt trip Kurumi into going out with her, despite knowing Kurumi isn't interested in her, and is likely interested in Naoi instead is all levels of messed up.
Kokoro's denial is now mixed with being delusional and filled with jealousy over Naoi. When Kokoro brought up Naoi in chapter 6, Kurumi seemed interested to know more and referred to Naoi in a familar way with no honorific, meaning they are close. Yet despite this, Kokoro assumes all of Kurumi's negative emotions are because of Naoi and wants to keep them apart. Kokoro is acting in self-interest here and justifying it to herself, as well as scapegoating Naoi in the process. Who knows if Kokoro plans to create problems for Naoi going forward.
Kokoro's eyes also took on a concerning look when she was caressing Kurumi's face. It's like Kokoro went into some kind of obsessive trance.
The rabbit symbolism also isn't healthy. It's like Kokoro wants to control Kurumi like she's a rabbit, taking away Kurumi's agency. This is bad for Kurumi in several ways. She already has very little agency due to her mother and now Kokoro will be doubling the pressure. Kurumi was already starting to break down at the very start of chapter 1, so that's likely going to lead to some negative things.
Kurumi responds to excessive pressure by rebelling. Well, how does one rebel against a romantic relationship? Cheating. Treating your partner disrespectfully. Avoiding them. And given Naoi's role so far and her current desire to help Kurumi break out of her rut, she'll obviously do everything she can so that Kurumi goes the extra mile. This will likely lead to Kokoro snapping (possibly violently) and blaming Naoi for corrupting Kurumi or making her do things, when really, Kurumi is just lashing out at the people putting pressure on her.