That Time I Got Reincarnated as a Slime Season 4 Reveals Key Visual, Trailer, April 4 Premiere
That Time I Got Reincarnated as a Slime Season 4 revealed a new key visual, trailer, and an April 4 premiere date. As previously announced, the anime will run for five cours, with the first two running consecutively.

The theme songs will be performed by Eir Aoi and CiON. Studio 8bit is animating the new season of the popular series with Naokatsu Tsuda as the director.
That Time I Got Reincarnated as a Slime is based on a Japanese light novel series written by Fuse and illustrated by Mitz Vah. The series also has an ongoing manga adaptation by Taiki Kawakami.
The TV anime adaptation by 8bit has three seasons, a spin-off anime titled The Slime Diaries: That Time I Got Reincarnated as a Slime, which adapts one of the manga spin-off series, seasonal special episodes, and a three-episode Coleus’ Dream side-story OVA. The newest installment in the franchise, That Time I Got Reincarnated as a Slime: Tears of the Azure Sea movie, premiered in Japan this February.
The main TenSura anime adaptation follows the manga serialized in Kodansha's Monthly SHONEN SIRIUS, not the light novel. Crunchyroll is streaming the anime.
Source: Official Website
© Taiki Kawakami, Fuse, KODANSHA/"Ten-Sura" Project