Dr. Gia came to Japan to perform a complex operation on a little girl whose serious illness was untreatable by Japanese doctors. He arrived late due to problems in traffic, and Sailor Aluminum Seiren, disguised as a nurse, tricked him into following her into an alley. Once there, she extracted his Star Seed, but was disappointed to find that it was a blank. Dr. Gia then transformed into a Phage, and in his new form, Sailor Doctor proceeded to attack Sailor Mercury and Eternal Sailor Moon, both of whom arrived after Sailor Aluminum Siren's departure.
After trying, and failing, to give Eternal Sailor Moon a "shot" with the huge hypodermic needle that made up his right arm and served as a stabbing weapon, he was incapacitated by Sailor Mercury's Mercury Aqua Rhapsody long enough for Eternal Sailor Moon to use Starlight Honeymoon Therapy Kiss on him, restoring his original form.