She was in charge of the Crystal Seminar, a cram school that Ami attended. The students were given special disks to use, not knowing that the disk would activate a program that would drain their energy. Usagi discovered the disk after a new student, Ami, left hers behind. Suspecting Ami to be from the Dark Kingdom, Usagi disguised herself and infiltrated the school.
Usagi confronted Ami and transformed into Sailor Moon, but then Garoben appeared, grabbing Ami by the neck and taking her hostage before transforming into her Youma form. While holding Ami, she first puzzled Sailor Moon with math questions before sending dozens of razor-sharp test sheets at her. Sailor Moon managed to dodge them, but ended up in a corner. Garoben asked if she wanted to surrender now or later, before the hypnotized, energy-drained students began surrounding Sailor Moon.
While Sailor Moon was busy fending off the students, Garoben forced Ami to look at her computer screen in an attempt to drain her energy, only to find it ineffective. Garoben threw her to the ground, and morphed her left hand into a large axe. After managing to dodge the first swing of the axe, Ami transformed into Sailor Mercury. Garoben wound up for another strike, but became lost in the cold mist created by Mercury's bubble attack. As she began shivering, the hypnotized students collapsed, freeing Sailor Moon and allowing her to use her tiara to destroy Garoben.