Neku was by no means a very good tracker, so the only reason he was tagging along with this team is if they caught up to the guy and started questioning him then and there. He was lucky he ran a lot, otherwise there would be no way he'd be able to keep up with them.

He's been hovering at the back of the group, trying to distract Shiro's... 'aura sense' or whatever it was as little as possible, even though the small amount of distance probably didn't do anything. Whatever. He'll just be here, a hand on his fire pin just in case, until he's needed.