How do you get manaphy to join your team in Pokemon mystery dungeon explorer of time?

you have to go to the surrounded sea and when you get to the end you will find 2 deluxe boxes and an egg. take the egg and you will get manaphy! After you defeat darkrai do a few missions(manaphy won't come back if you don't do missions) the chatot will tell you that manaphy came back and manaphy will ask to join your team.