After Ace confirms the Sword Heart, he searches for any information about how someone can achieve it or any clue. But to his dismay, there wasn't any information about it all, and there was just information on the vague concept of Sword Heart's ability.
However, it wasn't like all hope was lost; he had all this knowledge the imperial school had collected over thousands of years, so he had to go through all of it patiently, and who knows, he might find something.
Still, now that he knew that the Sword Heart was a mystic ability of sword path, Ace decided to use one of the insight pills to mull over the sword law he comprehended till this day and also the Sky Sword Manual, the highest law art he had except for the Heaven Sundering Sword.
Now that Ace thinks about it, the Sky Sword was created by a Sword Emperor named Executioner Sky Sword, and Ace didn't believe that someone calling himself Sword Emperor would not know about the mystic abilities.