The Quintessential Quintuplets: Sister Link

Ayaha, a lonely, withdrawn boy, makes a wish at a sea god’s shrine for a little sister to keep him company.

So on the first day, he gets his first little sister.

On the second day, a pair of twin little sisters show up at his house.

On the third day, a magical-girl little sister falls from the sky, bringing a mutated monster along with her. And so begins the story of a magical girl who blackmails a boy into fighting monsters??