The distance between them and the creature that was chasing after them was continuously closing in. And at the same time, the amount of energy that was contained within the golden light was also reducing.
But after Samuel managed to improve his level to the 6 star level, the same happened to Thunder. Having gone up a level, it was normal that Thunder's speed would also increase.
Additionally, due to the breakthrough, the energy that thunder had spent all this time finally recovered. So, it implied that Thunder could use lightning flash for longer.
This time, every time that thunder used lightning flash, he was capable of increasing the gap between them. But, the gap only decreased by a small margin.