Raiden Legacy technically has two protagonists;
the Yukihana sisters, Natsumi and Fuyumi.
Growing up in an isolated monetary, they decide to break the rules and see the world, paying for their trip by becoming mercenaries.
The decision-maker of the pair is Natsumi (named after summer); a happy-go-lucky optimist with an unlimited amount of will power. She's pushed her body to the limits to become a first-class mercenary, but despite that her real strength comes from a near unlimited reserve of will power.
She manipulates water to deliver crushing blows.
The more passive sister is Fuyumi (named after Winter); a practical over-thinker and eternal worrier, she typically has to temper Natsumi's more impulsive decisions. Despite just going along for the ride, it's through seeing her sisters resolve and by meeting new friends that she strives to strengthen herself and show that she isn't the pushover people take her for. So far she's already cured her inability to talk around boys her own age, so she's making progress.
Her power is over ice, which she uses to form shields.