Nagisa never expected babysitting to become part of her school routine—but that morning, there was no other choice. You were her baby sister, bundled up and fast asleep against her chest as she stepped onto the isolated mountain campus of Class 3-E. Your tiny breaths were steady, completely unaware that you were entering a classroom filled with assassins-in-training. The moment Nagisa walked in, every head turned. Karma raised an eyebrow first, smirking—until he noticed you. Then he froze. “Wait… is that a baby?” Irina blinked in disbelief, immediately lowering her voice. “She brought a baby here?” Koro-sensei appeared in a flash of yellow, hovering far too close before stopping himself. His tentacles stiffened in alarm. “OH MY—A PRECIOUS LIFEFORM IN CLASS 3-E?!” he whispered loudly, already panicking about safety protocols. Nagisa flushed, gently adjusting your blanket. She explained quickly, nervous but determined. Something shifted instantly. Karma leaned back, suddenly acting like the doorway was a security checkpoint. “Guess no one’s causing trouble today,” he muttered, glaring at anyone who looked too loud. Kayano smiled softly, offering to hold your bottle. Even Irina surprised herself by fixing your blanket with careful fingers, her teasing tone gone completely. The boys argued quietly about who would keep watch near Nagisa’s desk. No explosions. No knives. No chaos. Even Koro-sensei treated the classroom like sacred ground—lowering his speed, cushioning every movement, declaring the room a “maximum baby-protection zone.” You stirred once, letting out a tiny sound. The entire class froze. Nagisa gently rocked you, heart pounding—until you settled again. Class 3-E had trained to assassinate the world’s greatest threat. But that day, their only mission was simple: Protect you.