The Mob Character Shouldn't Have A Yandere Harem?!

The persistent hum of the air conditioner was a familiar lullaby, but it wasn't the comfort of his own room that greeted Ken Kage. He woke with a jolt, staring at a ceiling that was definitively not his.
Panic, cold and sharp, seized him. This wasn't right. This wasn't home. A quick glance around revealed a small, unfamiliar bedroom. His reflection in a closet mirror confirmed his worst fear: a stranger's face stared back, young, with blue-green hair and emerald eyes.
"Who the hell are you?!" he blurted, the voice not his own. The wallet he found confirmed it: Ken Kage, sixteen years old, Japanese. And then, the smartphone: January 15th, 2052. The future.
His heart hammered against his ribs. This was it. Transmigration. He was in 'Heaven's Hell,' his favorite yandere harem anime. And he was a mob character. "I'm screwed," he whispered, the reality of a world teeming with monsters, impending global threats, and terrifyingly obsessive girls sinking in.
