Killua's been tagging along the whole time, but drawing very little attention to himself. The kind of invisibility that comes not from just being quiet, but from consciously and actively working to make sure that you blend into the background of people's senses. If you're not looking for him specifically, you might forget he's there at all.
He does stop at Maya's command, though. He doesn't know much about Maya's abilities, and is curious enough to see what she can do.
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He does stop at Maya's command, though. He doesn't know much about Maya's abilities, and is curious enough to see what she can do.