That Time I Got Reincarnated as a Slime (2018)

S03E18 A Throng of Visitors

After wrapping up his meetings with the kings of several nations, Rimuru travels to Engrassia to personally invite his former students to the upcoming festival. The children are overjoyed at the chance to return with him to Tempest. But their excitement is interrupted when the hero Masayuki shows up, changing the mood entirely.