Han Sen followed Six Paths, searching for the Geno Core Tablet that would allow them to enter the main battleground.
If he couldn't finish the trial of the main battleground, he wouldn't be able to leave. Staying in that realm, with the constant risk of encountering super Geno Battle Souls, would be dangerous. So he followed after Six Paths, who was an emperor. He didn't even need geno cores to kill the foes they encountered.
Along their way, Han Sen inquired about Heart Sword. Six Paths watched Han Sen give a performance, then advised him on many tips and tricks he might not have caught on to. Han Sen was able to learn a lot.
Six Paths was not very secretive about this, either. He was even willing to divulge hidden information to Han Sen.
"I'm looking forward to another battle with you. You still need to get stronger, though." Six Paths spoke with sincerity.