Laplace Comes Face to Face With Demon Lord Leon
Dengeki Online, a Japanese games-and-anime news site, published the episode 15 synopsis along with nine preview stills for That Time I Got Reincarnated as a Slime season 4. The write-up is only two sentences, and the second one carries the weight: Laplace and his companions, posing as "merchants from the East," have made contact with Demon Lord Leon in El Dorado.
Leon's corner of the map has been hanging over the season since April. The official season 4 introduction says the Demon Lord "begins to move for a certain purpose" in the golden land, and that a "hero" is about to awaken as the agendas of heroes and Demon Lords cross. The preview doesn't say what Laplace wants from Leon, or whether the merchant disguise holds up. We'll find out when the episode airs.
This is episode 15 of the current season and episode 87 of the series overall, carrying the title "Fuon na Kehai" (roughly "Ominous Signs").
Tempest Starts Acting Like a Real Country
The domestic half of the episode is one line in the synopsis: new comrades have joined, and the monster nation of Tempest is taking its first steps as a nation governed by law. That tracks the season's larger arc. After throwing its Founding Festival and opening diplomatic relations with other nations, Rimuru's nation is working toward a world where humans and monsters can live and prosper side by side.
Standing against that project, per the season introduction, are Granbell Rosso, a former hero who heads the Five Elders of the Kingdom of Siltrozzo, and his granddaughter Mariabel. The two advocate protecting humanity through domination, and their scheming puts them on a collision course with Rimuru. Daisuke Ono voices Granbell and Inori Minase plays Mariabel, alongside Miho Okasaki as Rimuru and Natsuki Hanae as Yuuki.
A JoJo Veteran Is Running the Five-Cour Season
Season 4 is directed by Naokatsu Tsuda (JoJo's Bizarre Adventure) at Eight Bit, the studio that has animated the franchise from the start. Kenji Yasuda serves as assistant director, Atsushi Nakayama supervises, Hitomi Ogawa handles series composition, Ryouma Ebata is the character designer, and R・O・N composes the music. For the current cour, the opening theme switched to Daoko's "TACTIC."
For episode 15 itself, the credits list a script by 漆原虹平 (likely Kōhei Urushibara), storyboards by Kaori, and episode direction by 筑紫大介 (likely Daisuke Tsukushi), with chief animation direction shared by a four-person team.
Looking Ahead
Season 4 is planned as a split five-cour run, with the first two cours airing back to back. The season premiered on April 3, 2026, in NTV's "FRIDAY ANIME NIGHT" block, Fridays at 11:00 p.m. across a 30-station national network, and the second cour started July 3. BS11 carries the show Saturdays at 10:00 p.m. Dates for the remaining three cours haven't been announced.
Internationally, Crunchyroll streams season 4, with new episodes arriving Fridays in subtitled form and with an English dub. The source manga by Taiki Kawakami, Fuse, and Mitz Vah runs in Kodansha's Monthly Shonen Sirius and is published in English by Kodansha USA, while Fuse's original light novels are available from Yen Press.