"System, explain to me how in the world I have a 'True Name' like a Primal Spirit. What is going on?"
Ace hasn't forgotten about the disruption during the Primal Bond and almost incurred Pixy's wrath over it. But he wasn't at fault because he had no idea he was a 'True Name' carrier. He didn't even know the difference between 'worldly' name and 'True Name'.
This revelation reeled Ace; if not for his quick thinking, he knew he would've suffered terribly. He didn't ask Pixy because he could sense she needed rest, and she was forcibly keeping herself calm to answer his doubts.
Although she seemed to have recovered slightly after binding with the Thief's Space, it wasn't enough, so he let her rest.
But this matter regarding his true name was too important for him to miss, and if anyone might know the absolute truth, it would be the system since 'Heaven's Stealer' originated from it.