I left my genius brother for my own selfish revenge

Yua Inugami lives a happy life with her parents and newly born brother. this happy life was disturbed by her little brother learning how to use magic and succeeding, this was a rare accordance as not many people knew how to use magic and when her brother taught her how to use magic... their life change as their family was killed by a powerful beast. The brother and sister travel a long path to be separated a month after arriving in a nation. Yua had broken a promise to her brother fo her own selfish revenge.