What Should We Do with the Weakest Demon King Who Lives in the Demon King's Castle?

After traveling to another world, Phoenix's luck cannot be said to be good, only poor. When others think of me as a devil, either I don't eat beef or I have a harem of three thousand beauties. The demon king he became was not even as powerful as a goose, and the system was useless, without even a single loyal subordinate. This start left Phoenix speechless. But no matter what, he has to survive in this crisis-ridden world.