That Time: I Got Reincarnated As A Slime S01e245...
The episode you are referring to is titled (Japanese: Kanwa: Verudora Nikki ), which is technically Season 1, Episode 24.5 of That Time I Got Reincarnated as a Slime . Episode Overview Title: "Tales: Veldora's Journal". Type: A recap special that concludes the first season. Release Date: March 26, 2019.
It provides a rare look at Veldora's humorous and somewhat "tsundere" personality while he remains sealed. That Time I Got Reincarnated as a Slime S01E245...
Much of the comedic value comes from Veldora making up illegal rules (like promoting a piece to an "Emperor") because he refuses to lose to Ifrit. The episode you are referring to is titled
That Time I Got Reincarnated as a Slime (TV Series 2018– ) - IMDb which is technically Season 1
