The third season of Tensei Shitara Slime Datta Ken. 
Rimuru has officially become a Demon Lord after defeating Clayman. Following Walpurgis, the Demon Lords' banquet, Rimuru's domain is expanded to include the entire Great Forest of Jura. Anticipating a flood of representatives from all races showing up to pay their respects, Rimuru decides to throw a festival to commemorate the opening of Tempest, using it as an opportunity to gain new citizens and present Demon Lord Rimuru to the world. Meanwhile, in the Holy Empire of Lubelius, home base of the monster-hating cult of Luminism, Holy Knight Captain Hinata receives a message from Rimuru. But the message is actually a fabricated declaration of war sent by some unknown party. Upon learning that Hinata is heading for Tempest, Rimuru makes a decision... Thus begins a new challenge for Rimuru, striving to distinguish friend from foe in his pursuit of the ideal nation where humans and monsters can prosper together. 
(Source: Crunchyroll)

Episode 72 - After the Festival

Episode 71 - The Labyrinth Is Opened

Episode 70 - Settling the Score with the Hero

Episode 69 - The Martial Arts Tournament

Episode 68 - Nation's Opening Festival

Episode 67 - Festival Eve

Episode 66 - A Throng of Visitors

Episode 65.5 - Digression: Luminus Memories

Episode 65 - The Lightspeed Hero

Episode 64 - Benimaru's Ordeal

Episode 63 - Audience

Episode 62 - Labyrinth and Storm Dragon

Episode 61 - Invitations for All Nations

Episode 60 - Festival Preparations

Episode 59 - Reconciliation and Agreement

Episode 58 - God and Demon Lord

Episode 57 - The Scheming of the Seven Days

Episode 56 - Misunderstanding

Episode 55 - Saint and Demon Clash

Episode 54 - Those Approaching

Episode 53 - Meeting of Both Sides

Episode 52 - Everyone Has a Part to Play

Episode 51 - Peaceful Days

Episode 50 - The Saint's Intentions

Episode 49 - Demons and Strategies

Episode 48.5 - Digression: Diablo's Journal

8-bit

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Bandai Namco Music Live

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Sony Music Solutions

Nippon Television Network

That Time I Got Reincarnated as a Slime Season 3