In front of them, a heavy black-iron grate filled the entire tunnel. Etched seals ran around the circumference, and thick bars criss-crossed the welded wire. Effluent flowed through easily enough, but there wasn’t a lock to break, or hinges to pry loose. The grate had been built in place; it wasn’t intended to come out.

Presumably it had been intended to stop someone breaking in to Kirigakure, but it was just as effective at forestalling an escape.

Raidou spared half a second to think, dammit, then marshalled. “Tousaki, up front with Shiranui.” And Hatake, but Raidou didn’t plan to say a name that recognizable anywhere on the island. “Can we get through it? Around it?”

Genma peered at the bars. “I could weaken the metal enough for us to break through. But I don’t know about those seals.” He pointed to a seal at shoulder-height, and glanced back. “Do either of you recognize that combination?”

Ryouma edged carefully past Raidou, trying to avoid touching the slimy walls in this narrow section. There was a lot of sloshing. He leaned over Genma’s shoulder to squint at the seal. “I don’t recognize any of these. Is tunneling through the rock an option?”

Kakashi had a hand hovering, palm down, close to the wall. “There’re seals here, too, behind the rock. And in the ceiling. And the floor.” He dropped his hand, scowling. “Without getting a closer look, I don’t know what they’re set for — but destroying one in the last tunnel almost collapsed the whole thing.”

Ryouma gave him a quick, sharp look.

“I veto cave-ins,” Raidou said.

Genma shook his head, agreeing, and turned to Fukuda. “You’re a jounin and this is your country. What do these seals do?”

Fukuda held the glo-stick closer, casting green shadows across the grate. In the sickly light, the seals shimmered oddly. “That one is a chakra-inhibitor,” she said, indicating Genma’s seal. “These, lower down, are flash-sterilization seals — to decontaminate the waste before it enters the ocean.”

“That’s all very interesting,” Raidou said. “But how do we break them?”

“The whole point of chakra-inhibitor seals is that you can’t break them,” Ryouma said. He stooped to peer at the seal, frowning distractedly. “Maybe if you could work out a jutsu to eat the chakra powering the inhibitor seal…”

Kakashi made a quiet, dry sound. “Yes, let’s invent a new school of jutsu.”

“Does the inhibitor cover the entire grate?” Kimiko asked, from Raidou’s shoulder.

There was a short beat of silence.

“We’d have to activate it to tell,” Kakashi said at last.