After practice one afternoon, Yuji Kayama was approached by Chuuko Nezu, who tried to ask for an interview. When he refused, claiming that he was busy, she revealed herself to be Sailor Iron Mouse and removed his Star Seed. When it turned out to be a blank, he transformed into Sailor Guts. Usagi had been nearby when he was attacked, and she quickly transformed into Eternal Sailor Moon and confronted the Animamate. Sailor Iron Mouse promptly departed, however, leaving the Sailor Senshi to deal with the Phage.
Sailor Guts attacked with his "Youth's Perspiration Attack," which burned like acid wherever it struck. Sailor Jupiter arrived with the other Inner Senshi and used Jupiter Oak Evolution to block his attack, but the five Senshi were forced to run when he attacked again. The Sailor Starlights arrived soon afterwards, and Sailor Star Maker used Star Gentle Uterus to turn Sailor Guts' attack back upon himself. This stunned him long enough that Sailor Moon could use Starlight Honeymoon Therapy Kiss to return him to normal.
Sailor Guts was large and muscular, with short dark hair and heavy eyebrows, similar to his human form. His skin was pink and his ears were pointed, and he wore a skimpy outfit with a sailor collar and bow, briefs, and small angel wings on his back.
Youth's Perspiration Attack - Sailor Guts used an attack in which he threw large globules of sweat which both smelled foul and burned like acid upon impact.