Koi-Koi is a traditional Japanese card game played with a set of Hanafuda cards. The game typically involves two players who aim to collect specific card combinations to score points. Players take turns drawing cards and can declare "Koi-Koi" to continue playing for higher scores, risking their current points. The game features various flower-themed cards representing different months, each with unique scoring combinations. Players must strategize to create sets while also blocking their opponent's moves. Koi-Koi is popular for its blend of luck and skill, making it an engaging pastime in Japanese culture.