I'm not sure specifically about 'overlord sex fanfiction' but generally, fanfiction that involves sexual content is often controversial. It might deviate from the original intended story of 'Overlord' and can make some fans uncomfortable. Also, it may not be in line with the values the original work promotes.
It's mostly not acceptable. While fanfiction is a place for creativity, 'overlord sex fanfiction' crosses a line. The fan community is made up of diverse people, including children and those who don't want to engage with sexual content. Moreover, it can potentially damage the reputation of the 'Overlord' franchise. The community usually focuses on positive, respectful and creative expansions of the original story, not sexualized versions.
I didn't know that Overlord Lover was the name of a novel, nor did I know if there was an animation. If you can provide more information or context, I will try my best to answer your questions.
One interesting Overlord anime fanfiction could be those that explore the backstories of the minor characters. For example, a story about the daily life of an ordinary villager in the world of Overlord and how they perceive the powerful beings ruling over them. Another type might be fanfictions that put the main characters in different scenarios, like Ainz Ooal Gown having to deal with a sudden natural disaster in the game world that he wasn't expecting.
In most cases, the Overlord anime doesn't go beyond the manga. It relies on the manga as its source and keeps in step with it. There might be minor variations, but not to the extent of being ahead.
Overlord is about a powerful gamer trapped in a virtual game world as his overpowered skeletal character. He builds a dominion and faces various challenges and enemies.
In general, the Overlord manga does have more story content than the anime. However, the anime's adaptation is well-done and has its own charm. Some people prefer one over the other depending on their preferences.
The Overlord game was related to anime. Overlord was a light novel written by 486, which had also been adapted into an animation and game. In the game, the word 'overlord' referred to a powerful existence with power and ability that surpassed that of humans. The anime told the story of the conflict between humans and dragons, and also added superpowers, magic, and other elements.
There was no love story in Overlord anime. Although Overlord was a work with racial and fantasy elements as its theme, it did not involve love plots. The main character, Amber, was just a powerful warrior whose life revolved around battles and adventures. Although some characters had bonds and emotional exchanges, these feelings only existed to express their friendship and loyalty, and did not develop into a romantic relationship.