Dark Mercury

The transformation reworks nearly every element of her Guardian uniform into something colder and more elaborate. Her front knot abandons the usual loop for an ornate butterfly silhouette, while the collar and trailing ribbons swell into several puffy folds of black. A violet cast creeps into her hair, dark striping marks her boots, and the tiara adopts a black and purple scheme set off by an emblem unlike any other Guardian's.

Beneath the villainous shell, the isolation Kunzite exploited is what truly drives her turn. Feeling forgotten because her friends seemed absorbed in their own pursuits, Ami became easy prey for the Dark Kingdom's conditioning. Once converted, she shows open contempt toward her supposed allies, treating even Queen Beryl with scorn. Her buried devotion to Usagi never dies, however, and it is that bond, rather than any argument or blow, that eventually reclaims her. After she is restored, she carries heavy remorse, haunted by what she might have inflicted on her friends even though the memories are gone.

Her fall begins in Act 20, when a lonely Ami is ambushed on her way home by Kunzite, who materializes amid a scatter of dark rose petals and strikes her with a surge of energy that leaves her limp. By the following act she is bedridden and barely aware; Makoto nurses her and coaxes her to an amusement park, only for Ami to collapse on the carousel and land in the Juban municipal hospital. A crash from her room reveals the space wrecked and littered with petals, her body already gone. Drawn to Kunzite's stronghold and beyond Sailor Jupiter's reach, she invokes 'Dark Power, Make Up' through her Dark Jewelry Star Bracelet and rises as Dark Mercury, daring her former teammates to fight.

As an enemy she leans on brute force over spellcraft, being the Guardian with the fewest special techniques. She freezes an icicle into the Dark Sword, and in Act 22 unleashes a massive frost blast that fells Jupiter, Sailor Moon, and Mars at once. In her ordinary guise she keeps attending class, turning classmates against Usagi to cut her off socially. The conflict peaks in Act 27, where she overpowers Sailor Moon and splits the Moonlight Stick with her icy weapon just as the Silver Crystal nearly cleanses her. Standing over the fallen Usagi, the sight of her dearest friend broken jolts her memory loose; horrified, she flings the sword away and cradles her head as the tiara slips free and cracks apart on the ground.

The corruption ends in Act 28. Holding Usagi's still form, the depth of her affection overwhelms Kunzite's grip, and Sailor Moon's love restores her completely, costing the Dark Kingdom its captured Guardian. Ami wakes with no recollection of her time as the villain, yet she is consumed by guilt and dread over the harm she may have caused, a burden she only works through with her friends' support. Her ordeal closely mirrors the corruption of Mamoru Chiba in the earlier anime, where Usagi likewise saves someone she loves through devotion instead of combat.