Seuteulaikeo G

Eight years ago, an alien race known as the "Outers" appeared on Earth, met by the "Strikers"—individuals with special abilities who fight against them.
With the Outers launching daily attacks, life under the protection of the Striker Association has long since become the new normal.

In this world lives Kim Kang, who quietly (?) keeps his past a secret.
Then there is his older sister, Kim Yi-sol, who harbors eccentric hobbies like "harvesting Outers" and "dressing her younger brother up in women's clothing."
And finally, Cha O-young—a righteous girl who fights alongside them for the sake of peace, even though she doesn't quite trust the siblings.

This is the wild and boisterous school life of these three high school students.
[Source: Kakao, MTL]