Well, 'That Time I Got Reincarnated as a Slime' can be considered in this regard. Rimuru, the main character, experiences an isekai adventure, and there are some characters with possessive or extreme loyalty traits that could be loosely related to yandere. Also, 'Log Horizon' is an isekai novel where the characters' relationships and their growth in the new world might have some yandere - like undertones at times.
Well, 'yandere kanojo ga isekai novel' could potentially be a story where the female lead who is a yandere gets sent to an isekai world. Maybe she uses her yandere tendencies to get what she wants in that strange new world. It could be full of drama, as she might be overly protective of someone she likes in the isekai world, or she could be causing chaos because of her extreme love and possessiveness.
The 'isekai yandere novel' genre often focuses on characters with obsessive and possessive traits in the isekai setting. In contrast, other isekai genres may center more on adventure, power - building, or exploring the new world. For example, a typical adventure - focused isekai might be about the main character exploring dungeons and fighting monsters, while an isekai yandere novel will likely have a character who is overly attached or possessive of another, which can drive the plot in a different direction.
I'm not familiar with the specific details of this novel, but typically in such a story, the yandere kanojo would be a main character. There could be a male lead that she becomes obsessed with in the isekai world. And then there might be side characters like the local inhabitants of the isekai world, perhaps a wizard who helps or hinders her, or a group of warriors that she has to interact with depending on the plot of the novel.
One warning sign is excessive jealousy. Just like in the stories, if someone gets extremely jealous over normal interactions with others, like talking or being friendly. For example, if a person starts to glare or make mean comments when their 'target' is chatting with a coworker. Another sign is over - possessiveness. In real life yandere stories, they often act like the person they like is their property. So if someone tries to control where the other person goes or who they see, that's a red flag. Also, stalking behavior is a big warning sign. We see in the stories that yandere characters follow their objects of affection everywhere, and in real life, this is a very concerning behavior that should not be ignored.
One common theme is possessiveness. The yandere sister usually shows extreme possessiveness towards her brother or the main character. She doesn't want others to get close to him.
One common theme is overprotectiveness. The yandere little sister will go to extreme lengths to protect her loved one, often seeing others as threats. Another theme is possessiveness. She wants to have the sole attention of the person she's fixated on, like in many stories where she gets jealous of the protagonist's friends. Also, there can be themes of secrecy and hidden desires, where she hides her yandere tendencies until certain events trigger her extreme behavior.
If the situation becomes really bad, it may be necessary to involve authorities or get support from friends and family. A yandere - like person can be unpredictable, and having a support system in place can help protect you from any potential harm they might cause.
There was a case where a girl had a crush on a boy at work. She started to show yandere - like tendencies. She would leave anonymous love notes and small gifts for him. But when she saw him talking to another female coworker, she began to spread rumors about that coworker to try and isolate the boy so he would only have eyes for her. This created a very tense and uncomfortable work environment.
Well, 'A Sister's All You Need' also has elements related to the yandere sister concept. In this light novel, the sister's character has a certain possessiveness towards the main character, and through various events, it unfolds a story full of humor and family - like emotions.