This is the Apocalypse Stagnation Committee

Firing off massive guns to protect the world. That's our school life. Turns out our world is secretly in the middle of ending. Aberrations lurking in Ueno's Shinobazu Pond, a giant snail clinging to the Eiffel Tower, a demon lord who's clearly just a cute girl… The world is being destroyed by some occult something — the "Apocalypse" — whose true nature and numbers remain unknown. But behind the scenes, there are boys and girls giving it the finger and fighting back. "Ahaha☆ How dare a mere god hold its head so high before the ultimate beauty, Hikari-sama!" "Please hold back, Captain — you'll blow away the streets of Paris! If we're lucky!" They can't stop the Apocalypse. Can't eradicate it either. All they can do is make it stagnate. And yet they still pick up their guns. Why? Because for them, this is just another day, every day's a festival, and this is their youth! I used to be a grunt for the mafia, dreaming of a "normal" life. But here? Feels like a fun school life might actually be starting.