In general, it is legal to engage with Yu Yu Hakusho fanfiction. Fanfiction exists within a legal gray area in some ways, but as long as it adheres to certain principles. The fanfiction should be non - commercial (in most cases), and not be using the characters in a way that defames or misrepresents the original work too severely. Reading fanfiction on common platforms is a common and legal practice, as long as the platforms also follow the appropriate laws regarding intellectual property.
There is a bit of a love story in Yu Yu Hakusho. It's not the main driving force of the show, but it does contribute to the character development and adds some emotional complexity to the narrative.
There's also 'Naruto and Yu Yu Hakusho: A Shared Destiny'. This one is interesting because it delves deep into how the two worlds could co - exist. It's not just about battles but also about the characters learning from each other's cultures and values. It has a lot of character development and the writing style is engaging.