Stop expecting an OVA about a side character's past to matter. Tenpou's story rewrites what you thought you knew about the entire series. You watch a man become the reason everything falls apart, and by the end you understand why he had to. The manga author writing new material means this isn't filler, it's the answer to a question the original run never fully asked. A single episode that costs more emotionally than most full seasons.

Saiyuuki Gaiden: Kouge no Shou is a single-episode OVA that adapts chapters 11 to 13 of the original Saiyuuki Gaiden manga. The manga's author wrote additional material for it. The story is told through Tenpou's eyes, and the episode blends adventure, drama and fantasy.