Rin Natsuki appears as a tomboy and plays enough sports to have every team clamoring for her to join them but has always time for her family and friends. Her parents run a flower shop which she often helps in. Her alter ego is the Cure of Passion, Cure Rouge.

Rin is a girl who displays both tomboyish and feminine traits. She has a passion for designing accessories and is responsible for creating the designs for Natts House. Rin is straightforward and down-to-earth in her personality, which contrasts with the cheerful and optimistic nature of her best friend, Nozomi Yumehara. Rin takes on a nurturing role towards Nozomi and her siblings, often acting as a big sister figure.

Although Rin is usually straightforward, she can be hot-headed, impatient, and passionate at times, which can lead to clashes with more reserved and stubborn individuals. Rin's greatest fear is losing someone she loves, which is most noticeable in her attachment to Nozomi. Additionally, Rin has a fear of unnatural things, which stems from her childhood where it took her a long time to recover after being startled by such things.