"I see," Markus replied, letting his keyblade dissolve into the air.  "I've only seen one, I thought a person had to be inherently dark to fall like that."

He didn't say it aloud, but it frightened him to think that that could happen to anyone.  Could it even happen to him?  Or was his heart too strong to be taken?  He didn't know, but he hid his doubt in customary stoicism as they discussed the keyblades.