"It was the same spell that killed Goudai," Koumyou says, looking away. "I could feel it, just like the last time I watched someone important to me die. The last of nearly a dozen of us, all in my sight."

He folds his arms, and not into his sleeves like normal.

"And that was before I spent a year training him. Before he fully bonded with the Muten, and could use it to bolster that attack, a shockwave of nothingness as thin as blades.

"I knew the strength of it, before all of that. I knew how it had grown. I knew I couldn't put up a barrier strong enough fast enough, and we couldn't have outran it even if we'd started before he arrived. So, I used the only barrier left to me."

He finally looks at Genjo again, eyes hard in a way his son has never seen them. Koumyou Sanzo, the warrior.

"If I had gone on the offensive in that split second I did the math in, you would have died. Until I felt that spell, I had planned to counter-attack. The spell changed everything. Even the Seiten wouldn't have stopped it, it's not the barrier sutra. Not now that he'd learned to fuel it with the Muten. The Maten, perhaps, but I was never as fast with it, it would have been too late."