Lamune and Da Cider head off to Puff-Puff Palace to rescue two beautiful barely clothed maidens, Gold Mountain and Silver Mountain- the Mountain Duo. This of course infuriates Milk and Leska, who with a rather confused and unwilling Cocoa "transform" into "Seinaru Milky", "Seinaru Cacao", and "Seinaru Lemon". The three then head after their would-be boyfriends to extract their revenge.

When a motley band of travelling performers has a deep-space collision with another spacecraft, they find that the sole survivor of the other craft is a humanoid infant. They decide to raise the child as their own on the nearest planet as they wait for other members of the girl's race to come and find her.

Ifrit, who has been trapped in Rimuru due to the latter's Predator skill, recaps events of the season while in a discussion with Veldora as they play Shogi.

A summary of season one of Tensei shitara Slime Datta Ken with some extra content leading into season two.