I didn't know Cirno and Daiyousei can play chess at Super Grandmaster level.

The chess position in the drawing was a reference to the final game (Game 18) of World Chess Championship 2023, Nepomniachtchi vs. Ding. With only 60 seconds left on the clock, Ding famously refused his opportunity to draw the game and instead played 46...Rg6!, eventually winning the match.

The humor adds up since 46...Rg6! blocks the check from the opponent's queen, while self-pinning the rook to the king. It looks like an in-character, idiotic move that Cirno and Daiyousei would make. But it was the only available (and risky) move to reject the threefold repetition draw in this match.