The trainee medical ninja was named Serina, nineteen years old, the best at inserting needles in this year's Konoha medical class-and the worst at lying.
She noticed something wrong on the third day after Sakura sent her out on rotation: the backup battery in the Land of Hot Water's border mobile clinic had mysteriously charged itself to full three nights running. It wasn't a false reading caused by unstable voltage, but a genuine full charge, enough to run a portable chakra monitor for eight hours straight.
"Even the signal towers around here leak current. Who's charging your van?" her supervising Anbu veteran teased her for being paranoid.
Serina refused to let it go. On the fourth night, she deliberately cut the main switch before going to sleep. Rain woke her at midnight. Peering through a gap in the van, she saw the man in the gray coat who had spent the day crouching on the work shed, repairing its plastic roof. Now he was squatting beside a tire, holding two low-grade lightning-conducting wires salvaged from discarded Explosive Tags. With painstaking slowness, he wound one end around the chassis grounding point and laid the other in the rain-filled drainage ditch.
No hand seals. He was simply using a naturally occurring potential difference to give a dead battery a slow, hands-on charge.
"You..." Serina pushed open the van door, her voice trembling. "Did you use lightning-nature chakra?"
Lin Ye glanced back at her, gestured for silence, then pointed at the cheap cigarette tucked behind his ear. "I told you, stop assuming everything is chakra. On rainy days, there's a voltage difference between sheet metal and the ground wire. Middle school physics. I just made the wiring look a little nicer."
"But that wire came from an Explosive Tag-"
"Reusing scrap." He wrapped