Suné's Heartless

Suné's Heartless is a boss fought exclusively in the demo for Kingdom Hearts Symphony of Memories. It is the Heartless of Suné and is reason of Nexus's leave from The New Organization.

It is sometime referred to as "Unknown Heartless" or "Assigned Heartless".

Before Kingdom Hearts Symphony of Memories
Nexus was assigned to eliminate an unusual Heartless. When first spotted, the assigned Heartless appeared as a simple Shadow. But after being defeated, it evolve into a more powerful human-like appearance, shocking Nexus because of their similarities.

Instead going to Kingdom Hearts after finally defeating the Heartless, the heart hovers to Nexus, causing him to faint. After regaining consciousness, Nexus suddenly felt familiar emotions.

Trivia

 * Suné's Heartless is taken from Sora's Heartless, having similar traits and is able to evolve into different forms.