The owner

As Kretos was eating he looked at the owner of the Lonely Cat who was wiping a glass at the counter. Kretos couldn't sense any mana coming from the man. For him not being able to sense the mana of the other person could only mean two things, the man had perfect control of his mana that he's able to hide it from Kretos's senses, or the man had no mana at all that's why there was nothing to sense. 

The first reason seems a bit too farfetched as the way the bartender moved doesn't seem to indicate that he was a master or anything of the sort. On the other hand, the latter was nearly impossible, every living being born in this world is suppose to have mana. 

'Could it be he's not from this world?'