WARNING: The following contains spoilers for Episode 4 of Komi Can't Communicate, "It’s Just a Physical," now streaming on Netflix.
For the first three episodes, Komi Can’t Communicate has been focusing on Komi overcoming her social anxiety and especially her communication barriers. Her journey so far has been about connecting with her classmates and building friendships as a step forward. As of Episode 3, Komi has made three friends: Hitohito Tadano, Najimi Osana and Himiko Agari. Episode 4, however, throws a wrench in the works with the introductions of Makeru Yadano and Ren Yamai.
Both Ren and Makeru are toxic people in very different ways. Makeru is extremely competitive and hates losing to anyone in any aspect of life. It doesn't matter to her what that something is -- the perfect body, perfect eyesight, a perfect score in a game -- the only thing that matters to Makeru is that she beats everyone else in every category.
This drive to win is what put Makeru at odds with Komi: she's the most popular girl at school thanks to her good looks and was even made the "god" of her class by both the teacher and students. As such, Komi is Makeru's biggest threat to being #1, which is why she obsesses over besting her at a mandatory school physical exam.
The other new character, Ren Yamai, is a whole other category of toxic. Early on in Episode 4, she develops a crush on Komi, but it’s far from a healthy schoolgirl crush. The more time the episode spends with Ren, the more it becomes frighteningly clear her crush is actually an unhealthy -- and deadly -- obsession. More than anything, Ren's behavior throughout the episode points to her being yandere.
Like most of her classmates, Ren also loves Komi for her beauty. Whenever Komi walks through the halls or even just sits at her desk, she too does her fair share of fangirling. The moment Ren finds out Komi's friends with Tadano and Himiko -- students she considers losers -- she becomes frighteningly upset and decides to do something about it. The plan she goes with involves "eliminating" her competition so that she can have Komi to herself.
The first person Ren targets is Tadano, who she abducts on her way to school and imprisons in her bedroom. While bound and gagged to her chair, Tadano is horrified at the full extent of Ren's obsession as he sees the walls of her room plastered with pictures of Komi. It doesn't take long for him to realize that Ren's intentions aren't good.
At Itan Private High School, Najimi and Komi note Tadano's absence when they realize that he hasn't shown up to class prior to lunch. They immediately become suspicious of his whereabouts when they start noticing Ren sitting at Tadano's desk to be next to Komi. Since Najimi knows just about everyone at school, it's implied they're aware of Ren's history and especially her yandere behavior.
To confirm their suspicions that Ren is somehow involved in Tadano's absence, Najimi asks to drop by her house and invites Komi along. Totally aware of Ren's obsession, Najimi knows she won't refuse a visit from Komi. This would give Najimi the easy access to Ren's bedroom they wouldn't otherwise get. Once Komi and Najimi arrive, they get more than they'd bargain for.
Ren, not wanting to ruin her chances with Komi, she goes to her bedroom ahead of her visitors to hide Tadano in her closet, threatening to kill him if he so much as makes a sound. But she also threatens to kill him even if he doesn't. When Komi and Najimi make it to Ren's bedroom, Najimi takes advantage of Ren making tea to check her closet, where their suspicions are immediately confirmed.
When Ren returns to her room and sees her secret was discovered, she breaks and threatens to harm both Najimi and Tadano so she can finally enjoy a real friendship with Komi. Komi, however, simply writes in her notebook that she chooses her own friends, making it clear to Ren that she can't call the shots on her relationships. This shatters Ren, but it won't be the last Komi sees of her.
Komi's experience with Ren, unfortunately, leads her to believe that she's a danger to her friends and should cut ties with them for their safety. Tadano, echoing Komi's earlier confrontation with Ren, disagrees. He is friends with Komi of his own volition. When Ren returns to apologize for her behavior, Komi agrees to be friends with her if she stops threatening the friends she already has.
