Shion no Ou follows 13‑year‑old Shion Yasuoka, a talented Shōgi player who grew up in the shadow of a devastating tragedy. When she was five, her parents were brutally murdered in front of her. The killer sat her down, challenged her to a game of Shōgi, and demanded that she forget how to speak and the events of that night if she wanted to survive. Now mute but fiercely strong, Shion has entered the world of female professional Kishi. As her skill garners increasing attention, so do inquiries into her past and the brutal crime she witnessed. Gradually, her memories resurface, and the mystery begins to unravel, thread by thread.