The energy in Kaito's office was no longer one of frustrated waiting, but of sharp, focused planning. Kenji returned within the hour, his movements precise as he unrolled a series of old, dusty city blueprints onto the large table, right next to the high-tech digital map. The juxtaposition of old paper and new light was a perfect mirror of their new war.
"Aiko-sama was correct," Kenji stated, his voice stripped of its earlier skepticism, now holding only a deep, professional respect. He pointed to a spot on the blueprint of the Asakusa district. "The original 1950s architectural plans for that block show no sub-basement. But the 1980s utility refit," he tapped a different schematic, "shows an 'unregistered utility vault' built beneath the main structure. It's not on any public record. It's a concrete box, off the books."
Kaito's eyes narrowed, tracing the lines of the schematic. His face, which had been alight with the thrill of the hunt, grew dark again. "It's a vault, just as you said," he murmured to Kenji. "And look. No access point. No stairs, no elevator. It's a sealed tomb. The only way in would be from the warehouse's ground floor."
Master Jin stepped forward, his ancient eyes scanning the plans. "A classic fortress design. The Chinkonshi would have built the structure, placed their 'heart' within it, and then built the warehouse on top, sealing it in forever. The only entrance is through the main building."
The mood in the room plummeted. "And the main building is a death trap," Aiko finished, her voice a low breath. "The corrosive wards would destroy anyone who tried to get through the front door. So... we're back to where we started. We know where the 'off switch' is, but we can't reach it."
Kaito paced the room, his frustration a palpable force. "There must be a weakness. A flaw."
"A machine needs power," Aiko said, thinking aloud, her eyes fixed on the complex web of lines on the blueprints. Kenji had pulled all the utility maps. Power, sewer, gas... and water.
"It's drawing from the city grid, we assume," Kaito said. "But cutting the power to the entire district would alert every clan in Tokyo and might not even stop the heart stone, if it has its own internal source."
Aiko wasn't listening. She was remembering the feeling from the brick. The cold. The constant, pulsing cold. And then, she remembered her training with Kaito in the apartment, just before the J-Pop disaster.
"That day in the apartment," she said, looking at Kaito. "When Mochi... when the water spilled. It shorted out the entire smart-home system."
"Irrelevant, Aiko," Kaito said, his voice sharp with impatience.
"Is it?" she insisted, stepping up to the table. "That system was electronic. But this... this is magic. It's a massive spiritual engine, running 24/7. It must generate an incredible amount of... not just power, but heat. Spiritual heat. A by-product."
Master Jin's eyes widened. "She is right, Ishikawa-sama. A dark ritual of that magnitude, running constantly, would create a corrosive spiritual friction. It would need to be contained. Cooled. Or it would burn itself out, or even ignite, alerting the entire city."
"So how do they cool it?" Aiko asked, her finger already tracing a thick, blue line on the municipal water map.
Kaito and Kenji went still.
Aiko's finger stopped, tapping the map. "Look. The main city water intake for that entire district. An old, two-meter-wide iron pipe, laid in 1950. It runs right underneath the block... and it passes directly alongside the unregistered sub-basement."
Aiko looked up at Kaito, her eyes blazing with discovery. "They're not just using city power, Kaito. They're using city water. They've built their fortress against a giant, flowing, public utility, using the cold river water as a massive, constant heat sink to keep their dark magic stable."
Kaito stared at the map, a slow, dangerous, and utterly predatory smile spreading across his face. The Chinkonshi, in their arrogance, had built their impenetrable fortress on a foundation of flowing, public water.
"They built their wards to protect them from the air and the street," he murmured, the thrill of the hunt returning, stronger than ever. "They never expected an attack from below."
He looked at Kenji, his eyes gleaming with a new, audacious plan. "Get me a full schematic of the water tunnels. And find me the Ishikawa clan's best-hidden submersible gear."
The way in wasn't through the door. It was through the river.