FaceĀMonster Turn: The other three students turn into Oni after dying in version 6, and are just as dangerous as the regular Oni.
Extreme Omnivore: The monster can devour a rope ladder without blinking an eye.
Easter Egg: In the later versions, these can be accessed by entering different codes for Hiroshi's name.
By the same token, certain objects can be walked right through.
The oni suffers heavily from Artificial Stupidity in the original game, having a harder time navigating around obstacles.
Takuro leads this gang, and the other members include Mika's precursor Megumi, a brown-haired Takeshi counterpart, and a gray-haired boy who would eventually become Hiroshi in later versions. While the main character is still named Hiroshi, he's now a dark-haired underclassman who, along with the silver-haired Kazuya, gets forced to visit the mansion by a gang of four older students.
The original version puts more detail into the Excuse Plot with a longer opening sequence.
Dwindling Party: In some versions, including 1, 3, and 6.
He is extremely sad and guilt-ridden after convincing everyone to go into the mansion, only for most of them to get eaten, killed, or worse.
Driven to Suicide: Takeshi, in version 6.
Often times, this is the spot where players gave up on the game altogether.
Difficulty by Region: In version 5, there is a Japan-specific cipher puzzle which many non-Japanese players find almost impossible, even with the usage of a guide.
Darker and Edgier: Aside from removing the more confusing and misleading puzzles, version 6 amped up the horror elements compared to the previous one, changing the attic from just another location to get puzzle pieces into an Eldritch Location, including the gut-punching Scary Surprise Party scene, and sequentially killing off the other characters one by one.
Curiosity Killed the Cast: Depending on the version.
Cue the Rain: As you move deeper into the manor, you will eventually hear it raining outside.
Creepy Basement: The key location in all of the versions.
Conscience Makes You Go Back: In Version 1, this happens near the end of the game: Kazuya escapes, but goes back looking for Hiroshi.
Colour-Coded for Your Convenience: The Oni's Dark Blue color allows you to see it the millisecond it enters the room.
Color-Coded Characters: In the later games, Takeshi, Mika, and Takuro have blond, brunette, and red hair respectively, while Hiroshi has silver-white hair.
Then Double Subverted, seconds later, a monster with More Teeth than the Osmond Family and Black Eyes of Evil runs out from behind a bookcase toward the player. At one point, the player is in a room when something breaks offscreen, only to see a cat flee the room after knocking over a picture frame.
One of the first events in every game involves Hiroshi hearing a strange crash and going to investigate.
Broken Bridge: Most of the mansion's doors are locked at the start, forcing Hiroshi to explore and solve puzzles in order to progress.
Bookends: Two examples in Version 5's ending: Takeshi has a nightmare about being found in the cabinet he first hid inside, and a new group of victims enter the house.
In version 6, Hiroshi ultimately escapes, but couldn't save anyone, making for a Downer Ending.
In version 5, Hiroshi leads his friends to safety, but another group enters the mansion.
In 1, only Hiroshi, Megumi, and Kazuya manage to escape.
Behind the Black: The oni seems to like hiding behind text boxes to enter a room unnoticed.
Good luck trying to hide in one without the oni catching you! But if the oni is in the same room as you, going in one will land you an automatic Game Over (your hiding spot is no good when the oni sees you go in). You can escape the oni by hiding in one of them.
Awesome, but Impractical: There are closets in a couple of rooms.
Art-Style Dissonance: The character portraits in early versions are drawn in markedly different styles.
Sometimes Hiroshi might get to save everyone other times, not so much.
Anyone Can Die: Depending on the version.
Of which there are many included, especially in later versions.
Antagonist Title: The game is literally named "Blue Demon" in Japanese.
And Now for Someone Completely Different: In version 1, there's a point where the player switches over to Kazuya.
All Just a Dream: Used for both the Scary Surprise Party and a Catapult Nightmare in the fifth version's ending.
The oni disproves that theory, prompting a later dream where Hiroshi imagines he was right after all. This is demonstrated most in the third version even after being chased around by the oni, when he catches up with everyone else and gets asked what's happening, he suggests it's some sort of Halloween costume.