Centuries ago, mankind was slaughtered to near extinction by monstrous humanoid creatures called Titans, forcing humans to hide in fear behind enormous concentric walls. What makes these giants truly terrifying is that their taste for human flesh is not born out of hunger but what appears to be out of pleasure. To ensure their survival, the remnants of humanity began living within defensive barriers, resulting in one hundred years without a single titan encounter. However, that fragile calm is soon shattered when a colossal Titan manages to breach the supposedly impregnable outer wall, reigniting the fight for survival against the man-eating abominations.

After witnessing a horrific personal loss at the hands of the invading creatures, Eren Yeager dedicates his life to their eradication by enlisting into the Survey Corps, an elite military unit that combats the merciless humanoids outside the protection of the walls. Eren, his adopted sister Mikasa Ackerman, and his childhood friend Armin Arlert join the brutal war against the Titans and race to discover a way of defeating them before the last walls are breached.

Thirty years ago, the Eurasian continent was devastated by a supermassive "spatial quake"—a phenomenon involving space vibrations of unknown origin—resulting in the deaths of over 150 million people. Since then, these quakes have been plaguing the world intermittently, albeit on a lighter scale.

Shidou Itsuka is a seemingly average high school student who lives with his younger sister, Kotori. When an imminent spatial quake threatens the safety of Tengu City, he rushes to save her, only to be caught in the resulting eruption. He discovers a mysterious girl at its source, who is revealed to be a "Spirit," an otherworldly entity whose appearance triggers a spatial quake. Soon after, he becomes embroiled in a skirmish between the girl and the Anti-Spirit Team, a ruthless strike force with the goal of annihilating Spirits.

However, there is a third party that believes in saving the spirits: "Ratatoskr," which surprisingly is commanded by Shidou's little sister! Kotori forcibly recruits Shidou after the clash, presenting to him an alternative method of dealing with the danger posed by the Spirits—make them fall in love with him. Now, the fate of the world rests on his dating prowess, as he seeks out Spirits in order to charm them.