Aoki's Parasite

When Aoki's Parasite enters the battlefield, if
you cast it, you get 3 posion counters.
Aoki's Parasite's power and toughness are equal
to the amount of posion counters you have.
When Aoki's Parasite dies remove a posion
counter from each player. Then if you have one
or more posion counters, return Aoki's Parasite
to the battlefield under its owners control.