You could call them a 'fictional character enthusiast' or a 'fan of fictional characters'.
Well, one might say they are 'fiction character devotees'. This term implies a deep love and dedication towards fictional characters. It shows that they have a strong passion for these made-up personalities.
You could refer to them as 'fictional character lovers'. It's a simple and straightforward way to describe someone whose affection is mainly directed towards characters from fiction.
One common way to describe them is a 'story buff'. This implies that they are really into and have a great fondness for stories. Sometimes, they might also be called a 'story devotee', showing their dedicated love for the world of stories.
The term you might be looking for is 'fictional character affection'. It basically means having positive feelings and interest towards characters that are made up in stories, movies, or shows.
It's called being a 'fandom enthusiast'. When you like fictional characters, it means you're passionate about the fictional world they belong to.
It's called fictional attraction or fictophilia. It's when you have a strong interest or attraction to characters that exist only in fictional works.
Such a person is often called a 'novel enthusiast' or a 'bookworm'.
A person who writes fiction is usually called a fiction writer.
A person who writes stories is commonly called a 'writer' or an 'author'.
A person who writes short stories is usually called a short story writer.
Such a person is usually called a 'visual novel creator' or 'visual novel developer'.
Well, they could be called a 'fabulous story spinner'. This term implies that they have the talent to create and tell wonderful and captivating stories.