The Rune of Binding completed itself on a Sunday night, and Ryuu was afraid of it.
Not the way he'd feared the stray devils. Not the instinctive, animal terror of something that wanted to kill him. This was different. This was the fear of understanding something so clearly that you could see both its power and its poison.
Binding. The third rune of the first tier. The foundation's cornerstone.
Binding creates inviolable contracts between two parties or between a will and reality. What is Bound cannot be broken by force, by magic, by divine decree. A Binding lasts until its terms are fulfilled, its conditions met, or both parties agree to release it.
He understood now why the Codex had placed this rune last among the three. Stillness was defense. Negation was offense. Binding was architecture. It was the rune that built things, that created structures, that turned a momentary application of power into a permanent fact of reality.
And it was the rune that scared him because it was the same principle that the Evil Piece system was built on.
Contracts. Bonds. Agreements written into the scaffolding so deeply they became indistinguishable from natural law. Devils used them. Angels used them. The entire supernatural world ran on binding agreements, from the peace treaties between factions to the servant contracts that turned free individuals into pieces on a board.
Ryuu sat in the back room with the Codex open and his third rune fresh in his mind and thought about chains.
The Codex's version of Binding was different from the systems the factions used. Purer, maybe. Older, certainly. It didn't require hierarchy. It didn't require one party to be greater than the other. A Binding through the Codex was symmetrical. Both parties entered it willingly. Both parties bore its weight equally. And both parties could feel the contract as a physical thing, a thread in the scaffolding connecting them, taut and inviolable.
But even symmetrical chains were chains.
He closed the book and went upstairs and lay on his futon and stared at the ceiling. Three runes. Tier I complete. Stillness, Negation, Binding. The Carving, the Codex called this level. The beginning. The foundation upon which everything else would be built.
He should have felt accomplished. Instead, he felt the weight of what was coming. Because Tier I was the part of the Codex where the costs were manageable. Headaches. Nosebleeds. Mental fatigue. Painful, yes. Limiting, certainly. But recoverable. The pages beyond Tier I, the ones he'd started to glimpse in his sessions, described costs that were not recoverable. Costs that took things from you permanently.
But that was for later. That was for a future version of himself who had grown into something he couldn't see the shape of yet.
For now, he had to deal with the present.
And the present arrived the next morning in the form of Rias Gremory's entire peerage standing on the sidewalk outside Mikami Antiques.
Ryuu opened the shop at nine. Swept the front step. Turned the sign from CLOSED to OPEN. And there they were. Not threatening. Not aggressive. Just present, in the way that five supernatural beings standing in a loose semicircle on a residential street in Kyoto are present.
Rias in the center, her red hair catching the morning light. Kiba to her left, relaxed, hands in his pockets. Akeno to her right, her dark hair falling to her waist, her expression carrying the pleasant serenity of someone who could electrocute you while maintaining polite conversation. A small girl Ryuu hadn't met but recognized from his sensing, Koneko, compact and still and watching him with eyes that tracked the way a predator's eyes track movement. And behind them, slightly apart, a boy Ryuu's age with brown hair and an expression that suggested he was trying very hard to look like he belonged.
The brown-haired boy's scaffolding was different from the others. It had the signature of a devil, but underneath it, nestled in the deeper structure like a pearl in an oyster, there was something else. Something bright and layered and pulsing with a potential that didn't match his outward appearance.
A Sacred Gear. Dormant, or nearly so, but present. Massive.
Ryuu looked at the group and leaned the broom against the doorframe.
"I said I'd think about it," he said. "It's been three days."
Rias stepped forward. She was dressed casually again, and her expression was different from the careful composure she'd worn in the shop. Today she looked tired. Not physically; she was a devil, and fatigue didn't mark her the way it marked humans. But there was a tension in her jaw and a shadow behind her eyes that spoke of something grinding at her from the inside.
"This isn't about recruitment," she said. "Something's happened. I need your help."
Ryuu studied her. The scaffolding around her was agitated. Not the calm, dense warmth he'd felt before but something sharper. A vibration, like a glass about to crack.
"Come inside," he said.
The shop was too small for six people. Kiba stood by the door, keeping watch without being asked. Koneko took the chair by the counter, her legs swinging slightly, not reaching the floor. Akeno positioned herself near the back wall with the quiet competence of someone who always knew where the exits were. The brown-haired boy, Issei, Ryuu learned later, stood awkwardly near a shelf of teapots as if afraid of breaking something.
Rias sat in the customer chair and folded her hands.
"A rogue devil has entered the area," she said. "Not a stray. A political operator. Someone with connections to a faction within the Underworld that opposes the current leadership. They've been targeting independent humans with latent abilities. Testing them. And in some cases, removing them."
"Removing."
"Killing," Rias said. The word landed flat and heavy. "Three incidents in the past week, all outside my territory but within the broader Kyoto-Kuoh corridor. Humans with minor supernatural sensitivity, the kind who see ghosts or feel magical residue. All found dead. No trace of the killer. No energy signature."
Ryuu's skin prickled. "No energy signature."
"Identical to what we found at the parking lot. Zero trace. Whatever killed these people operates outside the three systems."
The room went very quiet.
Ryuu felt the connection form before he spoke it. "You think this is connected to me."
"I think it's connected to whatever you're using. The same anomalous signature. Either you're not the only one with access to this type of power, or someone is imitating what you can do." She paused. "Or the source of your power has other artifacts. Other fragments."
The Codex Primordialis, sitting in its box on the workbench six feet away, pulsed in Ryuu's awareness. Not literally. But the knowledge it represented, the understanding it had built in him, shifted at Rias's words, as if the book itself was responding to the suggestion that it wasn't unique.
"There's only one," Ryuu said. He didn't explain how he knew. The Codex was singular. The understanding it had imparted carried that certainty, the way the understanding of Stillness carried the certainty that motion was contractual. The Codex was one book, one manuscript, one artifact. Whatever was killing sensitives in the Kyoto corridor was using something else.
"Then we have a problem," Rias said. "Because something with a power signature identical to yours is killing humans, and if anyone in the three factions makes the connection between those deaths and your anomalous readings, you become the primary suspect."
Ryuu stood behind the counter with his hands flat on the scarred wood and felt the weight of what she was telling him settle into his chest.
He was being framed. Or coincided with. Or someone, something, was using a power that resembled his but came from a different source, and the bodies were piling up, and the factions were watching, and the window of time in which he could remain an interesting anomaly rather than a dangerous threat was closing.
"What do you want from me?" he asked.
"Help me find it," Rias said. "Your perception is different from ours. You can feel things we can't detect. If this entity operates outside the three systems, then conventional sensing won't locate it. But you might."
It was a fair request. Not a demand. Not a binding, not a contract, not a chess piece offered under the guise of protection. A practical exchange. Her resources, his perception.
"I'm not joining your peerage," he said. "That hasn't changed."
"I'm not asking you to. I'm asking you to help me prevent a war. Because if these killings continue and the factions trace the anomaly back to this region, the response will not be surgical. It will be territorial. And everyone in the crossfire, including you, including the humans you share this city with, will be caught in it."
Ryuu looked at Kiba, who gave him a slight nod. At Koneko, who looked at him without expression. At Akeno, who smiled. At Issei, who looked confused but determined.
And at Rias, who looked at him with something that wasn't quite desperation but was close to it. The look of someone who had been trained to command but was choosing to ask.
"I'll help you find it," he said. "On one condition."
"Name it."
"No Evil Piece. Not now, not during, not after. Not ever. Not as a suggestion, not as a last resort, not as a life-saving measure. I stay human. I stay independent. If I die, I die as what I am."
The condition hit the room like cold water. Issei flinched. Kiba's expression went carefully blank. Akeno's smile faded.
Rias held his gaze.
"Agreed," she said.
And Ryuu felt the word settle into the scaffolding between them. Not a Binding, not a rune, not a supernatural contract. Just a word. But a word spoken by someone who meant it, and received by someone who would remember it.
He stepped out from behind the counter.
"Show me where the bodies were found," he said.
The bell above the door rang as they left, one by one, and the shop stood empty behind them, and the Codex sat in its box in the back room, and the carved symbols on the box caught the light through the back window and held it.
The only piece that doesn't follow the rules of the board is the hand that wrote them.
Ryuu was learning to write.