Think about dark places or events. For example, if your story involves a cemetery, you could name it 'The Secrets of the Cemetery'. Also, consider using words that have a negative connotation, such as 'forsaken', 'cursed', or 'abandoned'. So, a title like 'The Forsaken Village' would work well. You can also play with words that suggest a lack of hope, like 'Endless Gloom' or 'Hopeless Darkness'.
One way is to look at the setting of your story. If it takes place in an old, abandoned mansion, you could have a title like 'The Dark Mansion's Secrets'. Another approach is to focus on the emotions in the story. If there is a lot of guilt, 'Guilt's Grip in the Dark' could be a unique title. You can also play with words that have double meanings related to darkness, like 'The Veil of Night' which not only refers to the night but also gives a sense of something hidden.
There's also 'Danganronpa'. Although not strictly a 'dark room visual novel' in the purest sense, it has elements of being in enclosed spaces which are often filled with a sense of dread and mystery, much like what you would expect from a 'dark room visual novel'. The story is centered around solving mysteries in these spaces while also dealing with complex characters and their motives.
One popular 'dark game novel' could be 'The Hunger Games' which has elements of a dark and dangerous game within its plot. Another might be 'Battle Royale' which is also about a brutal game where the participants fight to the death.
One popular 'dark earth novel' could be 'The Darkest Hour on Earth'. It might explore a post - apocalyptic earth filled with darkness, danger and survival challenges.
Some good examples are 'Dracula' which immediately brings to mind a dark and menacing vampire. 'The Shining' also gives a sense of something dark and sinister lurking in the hotel. 'Frankenstein' is another classic dark title that implies a dark creation story.
One popular 'dark side romance novel' could be 'Twilight' which has elements of the dark side with the vampire theme. Another might be 'Fifty Shades of Grey' which has some darker aspects to the relationship. There's also 'Wuthering Heights' where the love between Heathcliff and Catherine is full of passion and a touch of the dark side, like Heathcliff's vengeful actions.
Some popular ones could be 'Zombillenium'. It's a really cool story set in a theme park of zombies. The art style is unique and the story is full of twists and turns.