Karen

可憐

Karen is the first sister Wataru meets on Promised Island and is regarded as the story's heroine, as she appears to speak for all of them regarding how much they love and care for their older brother. She knows how to play the piano and is sweet, gentle, and generally a good girl. In the anime, she rescues Wataru when he first arrives and nearly drowns in the ocean, and they meet again soon after when he hears her play the piano at school.
In Sister Princess RePure, she adores her older brother as her hero after he makes a dress he gave her as a present more stunning than it originally was. It has been said that, out of all the sisters, Karen seems to have the strongest heartfelt and emotional connection with her brother. Supposedly, Karen is the only sister who is fully related to Wataru.