Starting to practice magic from Uchiha

As a non-Uchiha with only 1/4 bloodline, Uchiha Feiyu said that he didn't really want to be a demon, but who made the Uchiha clan force him to become a ninja?

It would be fine if I became an older ninja in the ninja school, but I just graduated and the Ninja World War happened. What's going on?

There is no way. Since they are going to force me to die, I can only become a demon. I can summon spirits and seduce souls, refine blood in the blood pool of all spirits, kill people and break lives to refine magic weapons... This damn world lacks everything, but there is no shortage of ninjas who want to die!