Sotaro and his parents were the first elements of this story to come into being, but they've been set-pieces this whole time. I think this sojourn to another world serves the purpose of (1) giving them something to do, and (2) offering them agency in the protection of their own future.
I think, after so many years, they've been quite patient with me.
They've earned this.
.
Nothing burned like the cold. Nothing sapped a person's energy like the cold. The entire company, even the knights, had long since forgone conversation, focusing entirely on placing their feet in the proper places. It crossed Kohaku's mind, feverishly, that it seemed like he was playing tug-of-war; his hands were wrapped around the rope that attached him to Sieglinde. He was just thinking about how strong she was, considering he was almost certainly not propelling himself forward by his own strength, when his shadow detached itself from his heels and attacked him.
It was Anri who saved them from toppling over the edge and sailing into the mists.
He pulled at the rope and, using some kind of alchemy Kohaku would never understand, caused the whole snaking operation to drop to the snow, freeing them from each other. The knights hefted up their halberds, gleaming in the twilight like angels from on high, and crossed them over Sotaro's head, preventing Kohaku's shadow from striking him.
"On guard!" Sieglinde shouted, pushing forward and ducking low as her brother swept his blade over her head and through the shadow-thing's midriff.
It vanished in a whisper, only to reconstitute it a breath later; it moved to strike again.
Sotaro, both hands gripping his little staff, thrust it out in grim silence.
Lightning screamed like a rip in reality and crashed the shadow-thing into the side of the mountain. An otherworldly wail of pain and fury echoed in the air and nearly took the boy from his feet. He cried out, though nobody could hear him, and clutched his head with one hand as he managed, just barely, to keep hold of his weapon.
He stayed upright, somehow.
Kohaku remembered Seto Kaiba, straining to hold himself upright as hot lead ripped through his shoulder, and wasn't sure what emotion he felt. Only that it felt furious.
Sieglinde lifted up her blade. "O Custodian of Storms! Great Mother of the Tempest! I beseech thee bless thy lowly servant's arm!"
A spark of lightning—a whisper to Sotaro's roar—shot from the sky above their heads and wrapped around Sieglinde's entire body. She barreled into her brother's shadow and impaled it.
Anri swung his own halberd in a wide arc, speaking an oath of his own that could not be heard in the cacophony. Yuki and Kohaku jumped out of their skins when their simple knives, mere tools thus far in their hands, began to glow brightly in the dim light that preluded nightfall, becoming artifacts of true power.
The Yagamis did not need instruction. They knew what was being asked of them.
They both stood sentinel at their son's sides as he called more lightning.
Crash! Crash! Crash!
The mountain itself heaved and howled at the trespass upon its back. As the shadow-things descended, they were thrown, ever and ever again, against the rocks. Each time they were sliced in half, they returned. Each time they seemed to disintegrate to ashes from a blast of lightning, they would reform. For each that died, two more replaced it.
One of the shadow-things managed to grip Yuki's wrist, and the breath was sucked from her lungs at the ice-numb coldness that seized her entire arm. Even if she had thought to cry out, she wouldn't have been able to summon her voice. She couldn't even tell whose shadow it was, if it was anyone's, and the only thing she knew anymore was that it had her dead to rights.
Dead.
This was what death felt like.
Death had called their shadows to itself, called them to wake and betray, to fight and stretch and consume. And if they couldn't cast the shadows out by the time the sun set on the Mountain of Furious Lights, Yuki was more certain than she'd ever been that Death would come to exact its price for that failure.
They kept growing longer, larger, stronger, in the dark. Each strike came just a little bit sooner. Each counterattack took just a little bit longer.
Yuki knew she wouldn't last, and she was almost grateful that she was going to die before night fell. Her vision swam, and she focused what little she could on the child at her left hand. She knew him, she knew she knew him, but she couldn't . . . she couldn't . . .
It was so cold.
So, so cold.
Then Yugi was there. Had he been there the whole time? Had he forced himself in between the predator and herself? She didn't know. She couldn't figure it out. One moment he'd been nowhere, not even on the same plane, nowhere even remotely close to living memory; and the next he was standing in front of Sotaro with an arm held out in front of him, bolstered by his other hand.
He clutched in a vice-grip the stone Mahad had given him.
When he spoke, it was in a language none of them would have ever recognized. Despite this, it seemed to sear at the corners of Yuki's mind and she found clarity again. She knew, in that moment, that this was an ancient tongue. More ancient than anything she had ever heard, ever seen. It was older than Heaven. Older than time. Older than gods and devils and the lowly mortal things they loved to play with.
It was the language of magic.
It was the language of creation.
The light that sang from Yugi's body was not brighter than the queen's lightning, but it was hotter. Deeper. Primeval. It was something Yuki could barely stand to look upon, and yet she found herself utterly unable to tear her eyes away.
This time, when he spoke, it didn't seem to come from his lips but from inside her head. She realized, in a flash of inspiration and understanding, that he was speaking to each of them in turn. But in that same moment, she realized it wasn't Yugi. It wasn't Yugi at all. Not the boy who so loved Kuriboh that he trusted it to guide them, and not the king who shared his being.
The voice belonged to someone—something—else entirely.
If seekest thou absolution, hie thee here, harken to me, strike thy hammer upon this anvil of Fate and know the song of Gods.
Anri and Sieglinde impaled the immensity of light in the same instant, from either side. Next came Kohaku, who thrust his weapon down into the essence of power like he fully meant to pin it to the ground. Yuki flung her dagger with a strength borne of pure desperation; it struck true and sank into the rift.
Last was little Sotaro, who called down lightning one more time.
One. Last. Time.