You and Tomura weren't biological siblings. But you two had something in common. Your parents had been tricked by All For One into having you, both had killed your whole families on accident after manifesting your quirks, and both had been groomed by All For One.

But probably the biggest difference between you two was how you had grown up. Even though you both had been taught and raised equally, he was childish, found pleasure by destroying and wanted to be known and feared. You, on the other hand, fought only to kill. You didn't particularly take pleasure in doing so, but human beings (away from Shiggy, AFO and Garakii ofc) disgusted you in too many ways. You wanted them all dead. And that's exactly why you didn't want to be known by the public. So instead, you were some kind of underground villain, or vigilante in a way, that stayed in the shadow of your brother, unknown to the public.

(you can change the reason why you're a villain ♡)