I'm in a Demon Sect, and the Empress Actually Taught Me to Rebel and Force Me into the Palace?

When Jin Changan woke up, he found that he had become a member of the Demon Cult. When he was melancholy and helpless, he unexpectedly picked up a ring, and the ring actually contained the remnant soul of a big sister. Grandpa Ring, right? Later, with the guidance of his elder sister, he made rapid progress and became a high-level member of the Demon Cult. Just when the leader was leading him to assassinate the current emperor, he was shocked to discover—— No, how did my ring eldest sister become the current empress?