"Sekigae Game" centers around a high school class subjected to a mysterious and unsettling social experiment orchestrated by their homeroom teacher. At the start of the school year, the teacher introduces a game called "Sekigae," which involves randomly shuffling the students' seating arrangements. However, the game quickly escalates into a high-stakes psychological battle when the teacher imposes strict rules and consequences for disobedience. The students are forbidden from communicating with one another outside of the game's parameters, and any deviation results in severe punishment, including expulsion or even physical harm.

The protagonist, a reserved and observant student, becomes increasingly suspicious of the teacher's motives and the true nature of the game. As the seating arrangements change, alliances form and dissolve, and the students are forced to confront their own insecurities, rivalries, and hidden agendas. The game's rules grow more complex and manipulative, pitting classmates against one another in a bid for survival and dominance. The tension escalates as the students uncover dark secrets about their teacher and the school itself, revealing a deeper, more sinister purpose behind the game.

Key characters include the protagonist, who serves as the moral compass and voice of reason; the enigmatic teacher, whose true intentions remain shrouded in mystery; and a diverse cast of classmates, each with distinct personalities and motivations. The narrative explores themes of power dynamics, conformity, and the fragility of human relationships under pressure. As the game progresses, the line between reality and manipulation blurs, leaving the students to question their own identities and the nature of their reality. The story builds toward a climactic confrontation, where the true stakes of the Sekigae Game are revealed, forcing the characters to make difficult choices that will determine their fates.