Duel all the ghouls and go the the park last. (where you duel Bandit Keith at the end)
Then go to Yugi his Toy shop, talk to Yugi. Then you two go to Kaiba Corp. Duel the Guard.
Go to the building and defeat Umbra and Lumis. Talk to Mokuba. Then go to the museum where you will find Seto. He will tell you Joey and Tea are in the neighbourhood of the pier.
Now the pier is unlocked. Go there, Fight Bandit Keith again. Go north to find your friend and at the end Fight Joey after Yugi telling you he cannot do it.