To write their character dynamics well, first understand their individual personalities. King is often more reserved and has a connection to nature, while Ban is brash and impulsive. Show how they contrast and complement each other. For instance, when they're in a fight, King might strategize while Ban jumps right in. Their banter should reflect this too. Ban could tease King about his more cautious nature, and King could roll his eyes at Ban's recklessness.
Highlight their shared experiences. They've both been through a lot with the Seven Deadly Sins. Write about how they rely on each other during tough times. Maybe they have a code word or a special way of communicating in battle. This shows their bond. Also, explore how they grow together. As they face new challenges, their relationship should evolve. For example, if King loses his confidence, Ban could be the one to boost him up, and vice versa.