Seeing Double

Seeing Double is a quest in Legend of Mana.

Premise
A mysterious doppelganger of the hero is causing mayhem in Domina. The nasty imposter is seen picking three leaves from an innocent Sproutling, threatening to come back when they regrow. It is then seen again plucking two leaves from another Sproutling in northern part of town, which causes the little plants to be scared to death by the main character. Inside Mark's House, the hero can see an evil Duelle try to coerce Teapo to give him her pumpkins back, saying he's going to use the bunch of squash to take over the world. He then threatens to make an itchy anthill on Teapo's back, which make the poor china creature cry, givng him all the pumpkins he wants. The delinquent takes its prize and leaves the place gloating. The same impersonator is then seen crossing Domina from west to east all the way through the pumpkin field. It is cornered by the real hero, but states that it is his/her dark side that hates him/her. It then transforms into Shadow Zero-One and attacks the protagonist. The shadowy monster is eventually defeated. Meanwhile, Mark comes by Teapo, saying that a shadow creature went aroun impersonating people and causing trouble, boiled up the Sproutling leaves, and grew an evil pumpkin patch. Realizing that she gave all her pumpkins to a fake Duelle, Teapo weeps for being relieved to see that Duelle is still a good guy.

Solution
Place the Sword of Mana in the space directly to above Domina to create the Tree of Mana. Do not enter the Tree of Mana yet. Instead, enter Domina.

Go to the center of town and you’ll see a duplicate of yourself doing bad stuff to a Sproutling. Go Right to the market. It will happen again. Go back to the center of town and talk to Teapo in the Lower Left door near the exit. Exit out of the building and follow your duplicate to the Outskirts of Domina. It will turn into Shadow Zero-One and you will need to defeat it.