When something (most often Japanese Media) is so messed up and/or disturbing that you can say with confidence that "only a Japanese person could think of something that gnarly"
The Anime, School Days, (and especially its ending) is the epitome of Japanese Gnar.
Otaku1: This anime is crazy! This chick had a miscarriage and went insane! She ate the dead fetus and merges conciousnesses with it and then she starts murdering a class full of elementary school students because she is jealous that other parents children actually survived! It's great! In the end an 8 year old kid cut open her stomach and removed the fetus, which then became a massive blob of evil that devoured the mother, and then corrupts the 8 year old kid, driving them insane.
Otaku 2: dude... that is some next level Japanese Gnar shit. You're making it sound like a masterpiece, it's just a bunch of sick perverted trash.
"a" hydrodynamic, city pop, apex predator shark from the city of Atlantis, who mostly feeds on salman (salmon) and shrimp. She now lives on land playing video games, streaming and doing other shark stuff. Gawr Gura refuses to return to Atlantis due to its lack of French fries, and now spends her time as a Hololive EN member who entertains chumbuddies. She dislikes hot sand and likes food, PWWIE as well as the color blue.
(Keep loud stomak away from her at all costs)
Person 1: Hey, what's your favoritetype of shark? Mine's the Hammerhead Shark.
Person 2: The Gawr Gura shark.
Person 1: What?
Person 2: Did I stutter?