The official Twitter account for the Kingdom anime series announced that the anime’s fourth season will premiere in spring 2022. A new visual featuring the character Sei Kyou with the tagline, “I’m next” was also revealed.
The third season’s staff includes Kenichi Imaizumi (After School Dice Club) as director, Noboru Takagi (Golden Kamuy Season 3) as series composer, Hisashi Abe (Psycho-Pass 3: First Inspector co-character designer) as character designer, Yusuke Mizuno (DOUBLE DECKER! DOUG & KIRILL) as art director, Miyuki Abe (The Morose Mononokean) as color designer, Daichi Nogami (Magical Girl Lyrical Nanoha Detonation) as photography director, and Hiroyuki Sawano and KOHTA YAMAMOTO (86 EIGHTY-SIX) as music composers. Pierrot and St.Signpost are the animation production studios.
The cast includes Masakazu Morita as Shin (Xin), Jun Fukuyama as Ei Sei (Yin Zheng), Rie Kugimiya as Karyō Ten (He Liao Diao), Kentarō Itō as Huan Ji, Yoshimasa Hosoya as Ōhon, Hirofumi Nojima as Mōten, Shirō Saitō as Biao Gong (Hyou Ko), Kenyū Horiuchi as Wang Jian (Ōsen), Taiten Kusunoki as Mōbu, Akio Kato as Tō, Yūya Uchida as Shun Shin Kun, Miou Tanaka as Kan Mei, Atsuko Tanaka as Ka Rin, Daisuke Namikawa as Go Hou Mei, Tatsuhisa Suzuki as Kou Yoku (Xiang Yi), and Yūto Uemura as Haku Rei (Bai Li).
Kingdom is based on the manga by Yasuhisa Hara, which began in 2006 and is still ongoing. The manga inspired a PSP game in 2010 and a live-action film that was released in 2019. The third season of the anime premiered in 2020, while the first two seasons premiered in 2012 and 2013 respectively. Pierrot produced all three seasons, with its subsidiary St.Signpost sharing animation production credits for the third season.
Crunchyroll describes the first season as:
Shin and Hyou are war-orphans in the kingdom of Qin. They dream of proving themselves on the battlefield until the day Hyou is captured by a minister. The boy manages to escape and return to his village, but he is badly injured. Shin then meets a mysterious youth who bears an eerie resemblance to Hyou—a boy who will one day become emperor!
Source: Kingdom anime Twitter account