Summer has come to Tempest. When he learns that summers here weren’t always this hot, Rimuru begins to fear that the change was his fault. Shuna and Shion have their own unique way to keep cool, and Rimuru tries to think up some fun summer activities… but bug-catching turns into bug-hunting when the bug he’s after turns out to be enormous, and a game of shooting water pistols gets out of hand when Rimuru himself becomes a water cannon. With everything on a completely different scale in Jura, every activity he tries turns into pure chaos! And Rimuru has no idea that he himself is the ideal cold pack…

Extreme summer heat is ravaging Tempest. Rimuru and crew visit a lake they’ve been told lies beyond the forest, and they change into swimsuits to start having fun… but Shion and Shuna seem dissatisfied with Rimuru’s swimsuit. Veldora watches the gang from inside Rimuru’s body as he plays a game of shogi with Ifrit. As the Storm Dragon, one who has never experienced swimsuits or water play, he struggles to understand what all the excitement is about…

In Great Sage's recollection, all seems to be smooth sailing for Tempest... but then the oldest of the Demon Lords, Milim Nava, arrives! Rimuru, as Milim's bestie, is appointed by the majority to be in charge of keeping an eye on her. With no knowledge of this, Milim explores Tempest and interacts more with the residents of the city of monsters... and Rigurd keeps track of all the damage she causes along the way in a report for Rimuru. "Rigurd... are you angry?"

If you use Shadow Movement to sneak into houses and a pegasus team to pull the flying sleigh... yes, in this world, it's possible to become Santa Claus! But... the Christmas tradition doesn't even exist in this world. When Rimuru tries to explain it in detail to the people of Tempest, they end up summarizing it as a "party." The Christmas cake and presents are ready, and most importantly, Kaijin and the other Dwarves create gorgeous decorations that bring the Christmas mood to Tempest. On top of that, Eren and the children treat everyone in town with their heavenly singing.