Han Sen put away the scale and rested. His wounds slowly recovered. He did not plan on returning to the geno universe for a while, and instead wanted to stay in the Alliance for a bit.
The Dragon were looking for him, and although Dragon Fifteen did not know Han Sen would teleport back to the same point he had left, Han Sen still thought it'd be a bit too risky to head back for the time being.
If Han Sen did not show up for a long time, and the Dragon could not find him in the Return Ruin Sea, it was likely they'd believe he had escaped entirely. When they let their guard down, it'd be much easier for Han Sen to slip back in and get off the planet.
The Dragon elites couldn't guard the Return Ruin Sea forever, so it was only a matter of time before they left.