Sunny Town of Summers
Turns out Pokey was here not too long ago and it is your job now to find out where he went and follow him. Unfortunately, you're stuck and the only way out now is by boat. There are boats in the port town of Toto which is to the east of Summers, but the captain won't let you on his boat until he fixes his marriage. His wife is at the Stoic club, but you can't get in without a reservation by phone. So go talk to people around town until you have the number. A Jamaican looking man inside a house will be the one to finally give you the number to the Stoic club.
Once you have the number, call it and enter the Stoic club. Inside you'll see a lot of people and a stage featuring a rock. Talk to the owner first and then talk to everyone else inside. The woman on the bottom right is the captain's wife. When you talk to her, she asks if you would like to try her Magic Cake. Agree and follow her outside. When you eat the cake, you will enter a dream-like trance and learn of a boy named Poo.
 Poo and Dalaam
This is the second and final time you'll have control of a character other than Ness. When you have control, grab the three presents on the side for a Brain Food Lunch, Brain Stone, and Cup of Lifenoodles and then save by talking to the man with phone-shaped hair. Head out to the east descend the mountain. The first house has a Bottle of Water in it. In the other two houses farther down you'll come across two more Bottles of Water, a Bowl of Rice Gruel, and a Jar of Delisauce.
At the bottom of the mountain to the west you'll see a group of ninja looking bunny statues guarding the cave entrance. You can't enter yet, so head to the east. Talk to the Star Master and climb up to the top of the cliff where you will now face a series of tests. If you try to do the tests on your own and fail, head down the mountain and go back to the palace to start over.
The first test has a girl calling to you to hurry back to the palace. Just ignore her and do not move Poo at all to pass the test. The next part of the test has a spirit coming to you. You'll be asked whether it can take away your body parts and senses. Answer "yes" to each question (don't worry about your HP dropping to 0, you won't die) and you'll pass the test and complete your Mu training.
Go back and talk to your Master and he will tell Poo to join Ness. You will gain a few levels and teleport to Summers, where the group is finally completely united.