Soldier Soldier Soldier, King 1 (S3K1)

The first season of the S3K anime establishes the core conflict between the titular Soldiers and the King, as well as building up the world's universe to the viewer. Fans have overall come to the agreement that this season is a required watch (despite being less exciting than later parts), as it sets up many significant plot points and character motivations which carry over into a narrative payoff in Seasons 2 and 3.