Kochira, Shuumatsu Teitai Iinkai.

Synopsis (en anglais)

Our world is actually falling apart, unbeknownst to most. A bizarre apparatus hiding in the depths of Ueno's Shinobazu Pond, a giant snail clinging onto the Eiffel Tower, a demon lord in the form of a beautiful girl... these and countless other cryptic entities—called "Ends"—are driving us closer to the apocalypse. However, some youngsters decided to reject that fate and secretly took up arms. They are fighting, not to stop the countdown or to eradicate the threats, but only to delay the inevitable. Why would they choose such a thorny path on their own volition? To make the most out of their youth in this godforsaken world! I, a former cartel slave (and ESPer), have had a pretty shit life so far, to be honest. But maybe here I'll be able to lead a fulfilling school life, at least? (Source: Kadokawa, translated)