Sepikimon says he knows a way to beat Zanbamon. He will tell you if you find his mask. Go to Baronmon in the Protocol Ruins. He says that he saw Sepikimon in Asuka City. Go there and you will see him. He says that he will not tell you because he found his mask. Go all the way to the Shaman's House. He says that was not him. Go all the way to Asuka City. Go to where the old man and woman are, near the big tree. You will see a Etemon. He is the imposter. He says Sepikimon went to Divermon Lake.