After making up his mind to infiltrate the humans' ranks and have taken him there themselves, Ace naturally came back to observe how these guys would react to this, and only then would he be able to plan accordingly.
But after seeing the entire thing played out, it would be a lie to say that he wasn't glad, and now he has a far better understanding of how these guys did not even trust each other, much less work together.
'According to the memories of that demon, the demon minister would most likely contact the Demon Emperor or that giant demon, for all I know. As for the devils, they will also be going to contact their respective Arch Devils, and the hunters will contact their elemental lords. As for the humans...' A cold glint flashed past his eyes when he thought that they would most likely be going to contact the Dream Shatter Ancestor!