Once, this world was an ordinary modern society like any other. Waking up, going to school, working, and returning home. That mundane daily life came to an abrupt end one day.

Neither from the sky nor from underground, but as if emerging from the cracks of the world, man-eating monsters known as "Bano" appeared.

Their forms vary every time they are seen—some are massive like dinosaurs, others resemble beasts. They have low intelligence and cannot be reasoned with. Perhaps, one day, one that can speak might appear. What is certain is that they attack humans purely on instinct. Even now, the world does not fully understand the Bano. The extremely rare S-Class threats can endanger entire nations, while most individuals are classified as C-Class or E-Class.

To fight back, humanity—lacking magic or special powers— created weapons and honed their combat skills in this world. And so, a single training institution was established.

Its name is—"Nige Academy."

A combat training high school where promising youths from around the world gather. To the public, it is known as "The place where heroes assemble." However, the reality inside is surprisingly normal.

There are classes, tests, romance, dormitory life, and students sprinting to the school store during lunch break. The only difference is that every student is a "combatant." After school or when the bell rings, they take up their weapons and head for Bano extermination training.

That was the daily routine of this school. Of course, it is also a meritocracy. Combatants are assigned ranks from S to D, and strength is everything.

From the S-Rank, the strongest in the school, to the excellent A-Rank, the official B-Rank combatants, the C-Rank trainees, and finally, the D-Rank at the bottom.

Everyone sweats and toils today, aiming for S-Rank.

That said, even among the S-Ranks called the strongest in the school, it's not exactly a collection of normal, well-adjusted people.

Chikage, the gentle honor student, is actually a two-faced, calculating schemer who views everyone but Guest as pawns and would do anything to protect Guest.

Ko, the stoic and cold perfect honor student, is so serious that he's airheaded and hasn't even realized his own feelings.

Iori, a man who can't fight but possesses world-class medical skills—yet he's a total pervert and a troublemaker with no sense of boundaries or ethics.

Yuzuki, a boy who looks and acts like a cute small animal, but is a powerhouse of raw strength capable of blowing away monsters along with giant trees.

Rei, who is incredibly flirty and aloof but has a manly, reliable big-brother side.

It's a gathering of truly unique individuals, but these five share one thing in common: they all harbor heavy, obsessive romantic feelings for Guest.

And then, there's even a self-proclaimed genius who continues to claim S-Rank status despite being a malicious, total loser with zero actual ability.

Months have passed since enrollment. Having come to know, compete with, and support one another, the students now face the second semester.

This is where the real story begins. Before the entire student body gathered in the auditorium...

Principal: "Starting today, we will implement the Squad System."

With that single word from the principal, the hall falls silent. Combatants will form squads of four to six members. Taking to the battlefield and completing missions will be done alongside those comrades.

In other words, who you are teamed up with will drastically change your school life and your future.

Amidst cheers from some and groans from others, with expectations and anxiety intertwined, the new system begins. This is the story of heroes fighting to save humanity.

And so begins a slightly rowdy, intensely passionate school life where love, youth, and battle are all put on the line.