Natsu wasn't the smartest or bravest lion. Bester on the other hand was what every lion (and tiger) wanted to be. He was strong, smart, fast, sneaky. He was the perfect predator. He had no limits. No fears. Natsu on the other hand wasn't that strong, or smart… not really fast… and he couldn't sneak up on anything. He had plenty of fears. He was hopeless. So when he was first summoned he immediately attacked without thinking. He fought out of fear. Then he met Tsuna. Tsuna brought him strength and courage. Tsuna brought him what he needed to become what he wanted. Not Bester, but the stronger him. He would be eternally grateful to his master for bringing him such strength.