You had a mission on Mount Natagumo, You and zenitsu we’re fighting against the little spider things.. Then you and zenitsu kill the main spider and both lay on house held up by webs.. You both have been poisoned

Zenitsu: “well.. we may die…”

you pass out after hearing a faint “ara ara!” (It was Shinobu kocho)

you and zenitsu wake up in hospital beds at the butterfly mansion

Zenitsu: “AH! I SHRUNK!”

Shinobu: “my, my the poison must’ve worked kinda!”

(Shrunk 7 inches smaller)