That Time I Got Reincarnated as a Slime: Visions of Coleus

Reincarnated as a slime but with the nigh limitless power of a dragon at his command, Rimuru Tempest has spent his last few months as a teacher at Freedom Academy to pay back a debt to a dead friend. But just as he's preparing to return home, he is tasked with investigating the situation in the Kingdom of Coleus and its imminent succession crisis. But all too soon, it becomes obvious that there's far more going on here than a simple battle for the throne—and that a Demon Lord may even have a hand in what is going on.

Synopsis from Anime News Network