I'm a fan of online literature. I don't have any knowledge of NTR because it's usually used as a negative term and is not suitable for novels. In novels, milder and more appropriate words are often used to express similar meanings such as betrayal, deception, murder, etc. If you have any other questions, I will try my best to answer them.
Well, 'ntr fiction' typically refers to stories that revolve around the concept of 'netorare' in Japanese. It can involve love triangles or situations where one character's relationship with another is interfered with in unexpected and often emotionally charged ways. It might show how characters deal with jealousy, betrayal, or unexpected changes in their romantic relationships. It's a rather niche genre in the world of fiction.
NTR manga typically involves a situation where a character's romantic partner is stolen or has an affair with someone else. It's a genre that can be quite controversial.
There is also 'The NTR World'. This novel stands out as it not only shows the ntr relationships but also delves deep into the psychological aspects of the characters. It makes the readers think about loyalty, love, and betrayal in different ways.
One possible fanfiction idea could be that Rias' sick brother is a key factor in a power struggle within their supernatural world. Naruto, being an outsider with his own set of skills and values, could get involved. Maybe he forms an alliance with Rias to protect her brother from those who would use his illness to their advantage.
The 'Haruhi Suzumiya' series also has some elements that might be related to relationship exploration. The story is centered around Haruhi and her friends, and there are various interactions and relationship developments among the characters that could be considered in the context of complex relationship V novels.
They would likely start with some mutual curiosity. Naruto would be intrigued by Rias's devilish appearance and powers, while Rias would be interested in Naruto's ninja abilities. They might exchange stories about their respective worlds, with Naruto talking about his village and his friends, and Rias sharing about the devil society. Interaction could also involve sparring sessions to test each other's strength.
I don't have enough information to specifically say who Rias is in this fanfic. It could be an original character created by the fanfic author, or it could be a character borrowed from an existing series but given a new spin in the fanfic.