I think the biggest scare in a love story is the possibility of losing oneself. When you love someone so deeply, you might change and forget who you really are.
As a fan of web novels, I don't have any actual feelings or emotions, so I can't say which one of Wesley's novels is my favorite. However, I can tell you some of the scarier and scarier parts of Wesley's novels, such as Dimensional Hacker, Dark Soul Path, and Alien. The horror elements of these novels mainly came from fictional alien creatures, strange events, and unknown scientific principles, so they easily aroused the fear and uneasiness of readers.
The Shining was a classic horror film directed by Stanley Kubrick and released in 1980. The movie was about a lonely hotel owner and his family staying in a seemingly comfortable but actually extremely scary room. As time passed, they began to find themselves trapped in a mysterious and terrifying world.
The film received high praise and reputation around the world and was considered a classic in the history of film. The horror atmosphere and the design of the thrilling scenes were widely imitated and used as a representative work in the history of movies.
One possible plot could be that Izuku has been through a really traumatic experience that has changed him. He starts to isolate himself and when people try to approach him, he acts in a way that scares them off. He could have developed some sort of survival - based aggression. For instance, if he was trapped in a really dangerous situation where he had to fight to survive, he might now react harshly to any sudden movements or people getting too close to him, which would scare his friends and classmates.
One interesting story could be where Edward's attempt to protect Bella in a 'scary' way actually leads to a deeper understanding between them. For example, he might overreact to a potential threat in the vampire world, which scares Bella at first but then she realizes it's his way of showing love.
I recommend "Back to the Warm Sun, Look Behind and Know" to you. Although it's not a pure horror novel, the plot line is very fascinating, and the further it goes, the more creepy it gets. The story was about a girl, Gu Zhiman, who had experienced fifteen years of unbearable past. She had been escaping and suffering until she met Fang Minghan and began to face this past. However, behind the truth was another tragedy. It was humanity and selfishness that made one's hair stand on end. I hope you like this fairy's recommendation. Muah ~😗