The game follows a bunch of high school students and faculty who are preparing for an upcoming School Festival, when they find they've been locked in overnight. And they soon discover that they aren't alone.
Now, the protagonist, an upperclassman named Inaba, has to explore the school, solve puzzles, and find a way out before he's killed by the mysterious forces in the building currently stalking them.
The game was released in 1998, but only in Japan.
After twelve years in devolopment; a complete fan-translation of the game has been completed, and is now possible to play in English for the first time.
...Iru! contains examples of:
- Cassandra Truth: When Inaba goes to Housou-sensei and tells her about Rie killing Kyoka, and then coming after him, she doesn't believe him.
- Darkness Equals Death: The characters don't start dying until the power goes out.
- Dwindling Party: Characters tend to die over the course of the game.
- Eaten Alive: Nakamura's fate.
- Eldritch Abomination: A couple appear in the game.
- Hirose looks into a mirror that summons a monster that sucks out his innards with a proboscis-esque tongue.
- A shoggoth is summoned in the hallway and eats Nakamura.
- A deep one will run into Rm. 3-5 and maul Inaba if he breaks open the crate there with the wrong tool.
- Half the Man He Used to Be: If you approach the shoggoth in the hallway, you'll be knocked to the ground and drug toward it. Then the camera shows Inaba missing the lower half of his body.
- The Many Deaths of You: Inaba can...
- Look into the same mirror that Hirose did, summoning the monster to suck his innards out.
- Approach the shoggoth in the hallway, and get bitten in half by it.
- Break open the box in Rm. 3-5, summoning a deep one to maul him.
- Missing Child: Mizuki comes to one of the teachers near the beginning of the game about his brother going missing three years ago when he was enrolled at the school.
- Neck Snap: After beating Kyoka up, Rie kills her in this manner.
- One-Word Title: Of course.
- Schmuck Bait: See The Many Deaths of You above.
- Spooky Painting: All over the school is one that looks like two purple faces being pulled apart, with some kind of sideways mouth full of sharp, yellow teeth between them.
- Total Eclipse of the Plot: There's a lunar eclipse occurring on the night you get locked in the school.