Xuanhuan: I, the Heavenly Demon Sect, Sign In for the World-Destroying Demon Scripture from the Start

The Male Lead Joins a Demonic Sect and Cultivates Its Techniques

The protagonist is the current leader of a demonic sect, secretly correcting orthodox cultivation techniques every day, and the sect's bigwigs still haven't noticed! Are you that good at hiding it, or are all the bigwigs undercover agents? I don't need the protagonist to kill people to cultivate. I just want the male lead to practice the sect's own demonic techniques. No stories where he takes in a few people and every single one turns out to be a prodigy.