Komi Can't Communicate is a charming rom-com anime series that takes place in a modern Japanese high school, and Komi Shoko's classmates are anything but ordinary. This series' manga and anime both include a wide variety of stock anime characters with minor twists to them, almost serving as an introductory class to how high school slice-of-life anime works.
This means Komi Can't Communicate has everything from high school culture festivals to shy dandere girls like Komi and Agari Himiko to the series' most troubling character, the classic yandere Ren Yamai. At first, it may seem odd that Komi keeps the company of a demonstrably unstable and harmful classmate, but Ren has a few meta-advantages keeping her in the picture.
The Plot Armor Of Ren Yamai In Komi Can't Communicate
In real life, a high school girl like Komi would refuse to keep the company of a yandere like Ren, especially in light of Ren actually kidnapping Tadano Hitohito in her house and her constant efforts to cross personal boundaries with Komi, such as trying to glimpse her undergarments. In a more serious drama anime such as A Silent Voice, a character like Komi would have distanced herself from Ren, and her parents would likely get involved as well. After all, Nishimiya Shoko's mother moved her to another school after Shoya repeatedly bullied her. Fortunately for Ren, the context of Komi Can't Communicate is a highly forgiving one, and the narrative gives her far more second chances than any other anime would.
The tone of Komi Can't Communicate is all about friendship, accepting other people for who they are, second chances and general happiness. Later volumes of the manga did set up a dramatic love triangle, but that was an exception. Otherwise, it would contradict the tone of Komi Can't Communicate to depict Komi or Hitohito bringing down the hammer on Ren and banishing her from the main group of friends, and the characters could never bring themselves to do that. Thus, Komi and Hitohito are a product of their environment, forgiving and easygoing people who simply cannot bear a grudge or think about revenge. For better or worse, this context shields Ren from any serious consequences of her actions, even if she locks people in her closet or tries to take photos of Komi's underwear.
The Novelty Of Tamed Villains In Anime
Ren might be given plot armor in Komi Can't Communicate for another reason -- the sheer novelty of having a tamed yandere character to take part in otherwise wholesome festivities. Plenty of anime series feature redeemed or relatively "good" villains who challenge the norms of what a protagonist should be, which can take the mystery out of these villains and show what their everyday life and thought process is like. Villains are usually only seen performing heinous deeds or delivering chilling speeches, which reveals only so much about them as people, and they rarely interact with anyone else positively. This includes yandere anime characters such as My Hero Academia's Toga Himiko and Future Diary's Gasai Yuno, but other yanderes and villains get a chance to step into a protagonist's shoes.
One example is the reborn villainess Katarina Claes -- originally a vain, spoiled bully who tormented Maria Campbell for years before experiencing the bad ending in the original Fortune Lover. Now, Katarina has the influence and appearance of a bad girl but not the personality of one. Viewers are treated to the novelty of the reformed villainess being an innocent, empathetic best friend to Maria and the others. Similarly, the isekai anime Overlord depicts a half-villain Ainz Ooal Gown befriending monsters like the succubus Albedo and the vampire Shaltear.
Now, Komi Can't Communicate's Ren is a somewhat tamed yandere who defied the odds and became a part of the heroine's circle of friends, and she refrains from the most serious yandere behavior such as stabbing people or setting buildings on fire. Granted, that doesn't conveniently absolve Ren of the bad things she has done, but her character is tamed just enough to make her a curious novelty in Komi Can't Communicate -- a partially de-fanged villain who gets more screen time than any other yandere would. Few, if any anime villains, could ever make it as far as Ren has.