After I Became a Calamity Beast, My Little Sister Became a Magical Girl

[Brother and Sister Dual Protagonists] [Humanoid Calamity Beast] [Magical Girls] [Witches]

[PS: Since this is a magical-girl world, the male lead has to use magic to disguise himself as a magical girl when he's weak early on, so he can move around more easily. Once he gets stronger, he'll return to his original identity. Some people have said there's a gender-bending element, though I haven't tagged it. Just a heads-up: if that bothers you, read at your own risk.]

With both parents dead, Xu Yichuan resolutely drops out of school to get a job and care for his little sister, who is still very young.

At eighteen, just after sending his sister off to school, Xu Yichuan catches the attention of the Calamity Church.

The Calamity Church is an organization bent on destroying the world. It often abducts ordinary people with no connections and subjects them to horrific human experiments.

The Calamity Church implants a magical device in Xu Yichuan: the Calamity Core.

From then on, Xu Yichuan becomes a humanoid calamity beast. He gains the ability to wield magical energy, just like a magical girl, and can also absorb the power of calamity beasts.

Just then, the Witches' Society invites Xu Yichuan to join them.

The Witches' Society is an organization of witches that opposes magical girls.

Persuaded by the society's leader, Xu Yichuan decides to join.

But at that very moment, Xu Yichuan's sister awakens as a magical girl.