The younger sister has been following the orders of her older brother who has become king in the King's Game for two days.

Mari has always loved her brother Tsuyoshi, who was good at studying and sports. He's now a frustrated and a NEET. One day, Tsuyoshi, who is retreating in her room, gives a suggestion. "Let's play the King's Game!" Mari ends up playing the King's Game with Tsuyoshi due to her extremely brotherly personality. And then Tsuyoshi, who has become king, receives an incredible order... "I will remain the king for two days starting today, so I will absolutely obey my orders!!"