As you can see right now Allen was going toward that direction where his target was staying right now. First of all it wasn't that far away from the Venus City so it won't take him that much time to reach there. But you can say at the same time he also knows why this mission was so important.
But naturally he could also understand most likely The guardian force was right now handling a far more greater threat than this, and because of this, until now they did not take care of this person. But at the same time he already gets to know that that person already gave some warning to the guardian force or you can say those newcomers of the guardian force. If they decide to attack him or do something like that then he will naturally release that monster.