המקרה בו חזרתי לחיים בתור רפש. Maybe

As Falmuth's army of 20,000 men marches toward Tempest, Rimuru takes hold of that hope and decides to become a Demon Lord
To see her wishes through, Rimuru leaves the Jura Tempest Federation and heads for the capital of the Kingdom of Ingrassia

Maybe

The probability of success is about 3%.

3
That Time I Got Reincarnated as a Slime
Swallowing his rage and grief, Rimuru realizes who their true enemy is and calmly questions Myulan instead of punishing her
המקרה בו חזרתי לחיים בתור רפש: Season 2 (2021) — The Movie Database (TMDb)
After enjoying a brief, peaceful respite, Rimuru tells everyone his future plans: he's going to get the word out to the whole world that he's a Demon Lord and declare war against Clayman
המקרה בו חזרתי לחיים בתור רפש: Season 0 (2019) — The Movie Database (TMDb)
He entrusts Benimaru and the others to destroy the devices that are generating the enemy's Prison Field while Rimuru himself sets out to attack the advancing army and use them as nourishment to become a Demon Lord
Meanwhile, the Jura Tempest Federation sends Youm out on a journey to make the world believe he was the champion who defeated the Orc Lord Ramiris seems to sense something about it
So Rimuru unleashes his new skill, Gluttony He travels around Tempest to see if his friends know of any good materials he can use, and he learns that a special type of sand found along a lake shore in the forest is exactly what he's looking for

המקרה בו חזרתי לחיים בתור רפש: Season 2 (2021) — The Movie Database (TMDb)

It turns out a demon has been revived, and the adventurers have been called to subjugate it.

המקרה בו חזרתי לחיים בתור רפש: Season 2 (2021) — The Movie Database (TMDb)
This story takes place before Rimuru's reincarnation
המקרה בו חזרתי לחיים בתור רפש: Season 1 (2018) — The Movie Database (TMDb)
Rimuru and his companions visit the Dwarven Kingdom, the Armed Nation of Dwargon, in search of some artisans to help the Goblins learn to supply their own food, shelter, and clothing
Maybe
This special episode gives some hints as to what's coming in the new arc, as well as a look back at Rimuru's exploits thus far
Amidst the uncertainty, the first to attempt the summoning is Gale, followed by Alice, Kenya, Ryota, and finally Chloe
The slime Mikami and the Storm Dragon Veldora decide to give each other names

That Time I Got Reincarnated as a Slime

Rimuru and the children reach the deepest level of the Dwelling of Spirits, where they stand on a pedestal bathed in light to summon superior spirits.

המקרה בו חזרתי לחיים בתור רפש: Season 2 (2021) — The Movie Database (TMDb)
In order to come to terms with his own negligence and revive Shion, Gobta, and his other fallen comrades, Rimuru reveals that he used to be a human
המקרה בו חזרתי לחיים בתור רפש: Season 2 (2021) — The Movie Database (TMDb)
That night, Rimuru has a dream in which he sees Shizu teaching children at her school in the Kingdom of Ingrassia—a dream showing Shizu's lingering regret
Maybe
One day, in the midst of the improvements on the Goblin Village with the help of Kaijin and the dwarves, Rimuru meets a trio of adventurers from the Guild who've been temporarily joined by a masked woman named Shizu