Mission 45: Collect hearts
Eliminate Heartless in Halloween Town and collect hearts.
Roxas continues his job to collect hearts for the Organization in order to complete Kingdom Hearts.
Head straight from the Entrance to the gate to see a short cutscene where Roxas notices a strange balloon. Continue to the Town Square where Jack explains the balloons to Dr. Finkelstein. Follow Jack to the Graveyard.
After the cutscene, you can start hunting for Heartless. First examine all of Jack's balloons in the Graveyard for Heartless. While these are easy to find, you'll probably need Zero's help to find the rest.
Around the Graveyard and the Town Square are bones that you can give to Zero. While Roxas is holding a bone, an icon will appear above his head, and the "Bone" command will replace "Attack". Approach Zero and select "Bone" to feed him a bone. For each bone he's fed, Zero will fly to a location where a Heartless hides. Find a search point in that spot. (It may take some clever jumping to find it.) While the reticule is visible, select "Examine" to find a Heartless.
If you give Zero a bone and he leaves the Graveyard, it means there are no more Heartless in that area. Follow Zero back to Halloween Town Square and continue feeding him bones to make him show you the locations of hidden Snowy Crystals. Use Fire spells to eradicate them. When you give Zero a bone and he leaves the Town Square, follow him back to the Entrance. Here, Zero points out one last Snowy Crystal hiding in a lamppost. Defeat it and the Mission Gauge should fill to 100%. Bid farewell to Zero and RTC!