This kind of 'fanfic' involves extremely unethical and disturbing content. Rape is a serious crime and violation of human rights in real life, and depicting it in fan - created works, even in a fictional context, is unacceptable as it promotes a negative and harmful view.
Another theme is self - discovery. As they interact, both Chara and Frisk might learn more about themselves. For example, Chara could discover a more positive side of themselves through Frisk's influence. In some fanfics, this is a central aspect of the story, with detailed descriptions of their inner thoughts and changes.
Another common theme could be the distortion of relationships. The relationship between Chara and Frisk is complex in the original game. In these fanfics, when Chara kills Frisk, it distorts that relationship completely. It could also lead to themes of guilt and regret, not just for Chara if the story delves into their emotions, but also for other characters who may have failed to prevent the killing.
It often starts with curiosity. They meet in the Underground and are intrigued by each other. As they spend more time together, they start to trust one another. For example, Frisk might show Chara the power of kindness, and Chara might show Frisk some of the secrets of the Underground.
One possible interpretation could be that it's a fan - created story within the Undertale universe where the character Chara kills Frisk. It might explore dark themes, such as the corruption of a character or a deviation from the normal storyline where these two characters usually have more complex relationships that don't involve such a straightforward act of killing.
There is also 'Chara's Perspective on Frisk'. This fanfic delves deep into Chara's thoughts about Frisk. It's really interesting as it gives a different view on their interactions compared to the original game. It shows how Chara might be secretly admiring Frisk's kindness and determination.
One common theme could be adventure. Since the Undertale universe (where Frisk is from) has a lot of adventure elements, it might be carried over into the fanfic. Another could be relationship development between the two characters, exploring how they get to know and care for each other.
Definitely not. Rape is a very serious and traumatic topic, and it has no place in fanfic. Fanfic is supposed to be a way to explore characters and their relationships in a more positive or creative way, not to spread such harmful and offensive ideas.
It should be removed. Such content is not acceptable in a healthy fan community. Platforms that host fanfic should have strict rules against this kind of inappropriate and disturbing content.