I am looking for a QT BL novel where in one of the worlds, the MC becomes a demon/spirit fox and travels around with his demon/spirit fox sister. He then later on stumbles upon the ML who is the general of an army, only to find out that ML has a lover. MC becomes heartbroken, runs away, and awakens his demon king powers along with his sister. Then there are... like... two factors in this world that goes to war with each other, and MC kills ML.