"Yes, that's correct," Officer Tomi confirmed.
"Temperature affects rigor mortis," Hayashi Shuichi continued. "That's why the killer set the air conditioner so low."
"Temperature?" Eri Kisaki asked, stunned. "Is that why the air conditioner was on?"
"Exactly," Hayashi nodded. "After death, muscle metabolism stops, glycogen degrades, producing lactic acid, lowering pH. This boosts ATPase activity, breaking down ATP into ADP, forming actomyosin, causing stiffness. High temperatures speed this up; low temperatures slow it down."
"Dr. Kobayashi, is he right?" Vice Principal Inoue asked.
"Simplified, but accurate," Dr. Kobayashi said, eyeing Hayashi. "How does a high schooler know this?"
"My adoptive relative, a doctor, had medical books," Hayashi lied smoothly.
"Evidence, Lin-kun?" Inspector Samezaki pressed.
"Condensation under the air conditioner shows it was running recently, set to 16°C," Hayashi said. "The judo club had no daytime activities, so it should've been off. Gym air conditioners are usually 26–28°C, as Kogoro confirmed."
"Right," Kogoro nodded. "I turned it off yesterday. It wasn't 16°C."
"Low settings cause cramps or colds post-exercise," the PE teacher added.
"It's over 30°C outside," Hayashi continued. "The air conditioner, set low, cooled the room, then stopped, letting hot air condense on the cold wall. That water is proof the killer used it to delay rigor mortis, creating an alibi."
"Right, Minister Hoshino?" Hayashi stared.
"Even so, why me?" Hoshino gritted his teeth. "Makino could've done it!"
"Makino's your scapegoat," Hayashi sneered. "You planned to stage Doi's death as suicide, but I exposed the strangulation. You used the air conditioner to delay rigor mortis for an alibi, but you were the last to see Doi at lunch. To shift focus, you named Makino."
"Makino vowed revenge, but he's not the killer," Hayashi said firmly. "Doi left evidence on you."
"Nonsense! Where's the proof?" Hoshino paled, instinctively covering his left arm.
"You lured Doi to the room at lunch, strangled him with a rope. He scratched your arm, leaving blood and flesh under his nail," Hayashi said, pointing to the fragments Officer Tomi collected.
"I didn't…" Hoshino stammered, retreating.
Inspector Megure moved to check his arm, but Hoshino threw him over his shoulder onto the tatami. Kogoro rushed in but was grabbed and nearly thrown. Recalling Hayashi's grappling tips, Kogoro tripped Hoshino with his legs as he fell, then pinned his neck.
Other officers piled on, forming a human pyramid to subdue both. Megure, recovering, cuffed Hoshino's hands tightly, then ordered the officers to stand.
"Almost crushed me!" Kogoro gasped. "Can't you try something else?"
"Sorry," Megure chuckled dryly. "Police academy teaches the pyramid method to restrain suspects."
Hayashi pulled up Hoshino's left sleeve, revealing a clear bloodstain.
"Anything to say?"
Hoshino's face twisted. "Hayato deserved it! He betrayed me!"
"You were friends," Kogoro said, confused. "You both excelled in last year's National Judo League. Why?"
"Because of Makino Shinji!" Hoshino spat. "He joined last year, but his judo talent outshone us both!"