Level 999 Demon Lord and a Level 1 Slime is a completed manga by Yoshinori Noguchi, first published in 2020. It blends fantasy and slice of life. You can read all 9 available chapters of Level 999 Demon Lord and a Level 1 Slime online for free on MangaPulse; the newest is Chapter 9, added 2022-08-21. The series is finished, so you can read it from start to end in one go.