Ultimate: the Demon King with over 100 Million Combat Power Has Retired?

Millions of years ago, he was the only human demon in the demon world. He alone is an insurmountable wall between the Twelve Spacetimes and the Demon Realm. For thousands of years, he suppressed the heavens and created the most prosperous era of the universe. Then he got tired. The Demon Lord sealed his body and his soul fell into reincarnation. In the past 100,000 years, he had become countless names - the Overlord of the Universe, the Lord of the Demon-Breaking Island, the King of the Dark Night... Each identity is a legend. Until this day, he woke up from his deep sleep, opened a convenience store, worked from nine to nine, sold drinks, collected change, and lived a retired life. But... Why is the world starting to tremble?