In Seii Daimyo, each player is an aspiring Daimyo with goals to unify the shattered Japanese islands under a new, great Shogunate. Each player has an identical set of role cards: 1 Samurai and 1 Ashigaru. Each round, players play one of these cards secretly and gain actions based on what they played, as well as what the other players chose to play. Seii Daimyo is played over a series of five rounds. Each round, several locations are revealed from the deck, and each player plays one of their role cards face down to try to strengthen their forces and increase their control over the three islands.