What if Kamijou Touma, the unlucky protagonist of A Certain Magical Index, had a younger sister?

Not just any sister, but a Tokiwadai honors student who's calm, collected, and practically a big sister to even Misaka Mikoto herself.

But there's a twist.

In this reimagining of the A Certain universe, that same younger sister harbors a hopelessly severe brother complex—so intense, she can’t even see Touma as just “family” anymore.

While Touma deals with saints, espers, magicians, and misfortune, his sister is battling something far more dangerous: her own feelings.

This is the story of the Kamijou siblings—where Imagine Breaker can’t block love.

I'm Tokiwadai's Top Student, but My Weakness Is… Oniichan?!