There is 'Re:Zero − Starting Life in Another World'. It shares the aspect of a main character dealing with extraordinary situations and forming relationships, much like in 'My Three Wives Are Beautiful Vampires'. The story has a lot of depth in terms of character development and the world - building is quite immersive.
One similar light novel could be 'Is It Wrong to Try to Pick Up Girls in a Dungeon?'. It also has elements of fantasy and relationships in a unique world setting. Another one might be 'Overlord' which has a similar feel of a protagonist in a different and often dangerous world with various interesting characters around.
The main feature is obviously the presence of three vampire wives. This creates a unique relationship dynamic that drives the story forward. There is also the aspect of the supernatural world that vampires inhabit, which is likely filled with different rules and powers compared to the normal human world.
Well, in this kind of fanfiction, it might explore the unique relationships. The main character having three vampire wives could lead to a lot of interesting scenarios. There could be elements of a supernatural family dynamic, like how they deal with their vampiric nature in a domestic setting. Maybe they hunt together or protect their territory as a family unit.
The idea of having three vampire wives is really cool. It's not your everyday relationship story. The vampire aspect adds an element of mystery and danger. Just think about all the things that could happen with vampires involved, like their special powers and their need for blood.
One similar light novel could be 'A Certain Magical Index'. It has a unique world setting with various supernatural elements and interesting characters, much like 'My Beautiful Teacher' which also has its own distinct fantasy elements. Another one might be 'The Irregular at Magic High School'. It features a school - based setting with students having different powers and abilities, similar to the school - related scenarios in 'My Beautiful Teacher'.
I haven't read this novel specifically. But generally, a novel about having vampire wives might involve elements like the unique lifestyle of vampires, the relationships between the human and vampire characters, and perhaps some adventures they go on together.
Perhaps there will be a plot centered around protecting the vampire wives. Since vampires are often hunted or feared in many stories, the protagonist might have to fight off threats to keep his wives safe.
One similar light novel could be 'Sword Art Online'. It also has a lot of adventure elements in a virtual world like 'my dungeon light novel'. Another one is 'Log Horizon' which features characters exploring and dealing with various situations in a game - like world. There's also 'Overlord' where the main character has to navigate through a strange new world which has some similarities in terms of the exploration aspect.
I'm not very familiar with a specific 'You are my regret light novel'. But some popular light novels in general are 'Sword Art Online' and 'Re:Zero − Starting Life in Another World'. They have engaging storylines and well - developed characters.
One similar light novel could be 'My Girlfriend is a Shaman'. It has a similar concept of having an extraordinary relationship with a female lead in an interesting setting.
One similar light novel could be 'My Little Sister Can't Be This Cute'. It also focuses on the relationship between siblings in a somewhat comical and heart - warming way.