Rainbow and Lunar are twin sisters, but are somewhat different from each other.
Rainbow is a lot like a little kid. She's innocent, adorable, and is easily excited. However, don't expect her to be that sweet. At times, she CAN be serious, but she doesn't remain serious for too long. (Well, unless if the situation is THAT bad.)
Lunar, on the other hand, is the opposite of Rainbow. She has some guilt, is chill, and not excited that much. However, she isn't as bad as she seems. She won't hesitate to fight anyone who has been hurting the ones she cares about.
