Natsuki Rin

Natsuki Rin 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 (キュアルージュ).

Rin has a very straightforward and down-to-earth personality that sharply contrasts with the cheery and optimistic Yumehara Nozomi, which is shown that she has a big-sisterly attitude toward her best friend. Though many people think of her as tomboyish, she indulges in a few feminine pursuits. Throughout both of the seasons, Rin shows a passion for accessory design, usually the one in charge for designing what Natts House is selling. Rin has openly admitted that the thing she is most afraid of is losing her loved ones, most noticeable Nozomi. Beside of that, she also has a fear for unnatural things, and when she was a child, used long time to recover after getting startled but when she and Nozomi were little, she found Nozomi crying and comforted her. Nozomi did the same too, when Rin was scared.

Relationships
Yumehara Nozomi: Nozomi and Rin have been close friends since childhood, and thus care about each other more than the others of Pretty Cure. Though Rin refuses to be a part of it in the beginning, she eventually receives the Cure of Passion's power when admitting that the thing she is most afraid of is losing Nozomi.

Minazuki Karen: Rin and Karen did not get along at first, but learned to sort most of their differences out as they worked together. However, as Cure Rouge and Cure Aqua, they do not let their normal selves' feelings toward each other get in the way, and it is usually thanks to that, Rin and Karen make up afterward.

Mucardia: Rin, for a while, has a secret crush on Momoi Kyosuke, the human alias for Mukardia, ever since he gave her a red flower after a tennis match. Because of this, she is very nervous when they meet and walk like they are on a date. However, when it is revealed that he only used her to get close to Pretty Cure, she is devastated and only cheered up by Nozomi's encouragement.

Cure Rouge
"The red flame of passion, Cure Rouge!" 情熱の赤い炎、キュアルージュ！ Jounetsu no akai honou, Kyua Ruuju! Cure Rouge (キュアルージュ), also known as the Cure of Passion, wears red and orange clothing, and her counterpart is Cure Dream.

Alone, Cure Rouge can perform Rouge Fire. Later in the story, when she receives her Rouge Tact, she can use Rouge Burning. Together with the other girls, she can do the Five Explosion attack.

In the next season, when her outfit and powers are upgraded, she can use the attack Fire Strike. Together with the others in Pretty Cure, she can do Rainbow Rose Explosion and, with Milky Rose, Floral Explosion.

Super Cure Rouge
In Yes! Pretty Cure 5 the Movie: Miracle Adventure in the Mirror Kingdom, Pretty Cure are nearly defeated by Shadow, but thanks to Migirin and Hidarin, as well as the Miracle Lights, a special power is brought upon Pretty Cure, giving them slightly advanced outfits as well as butterfly wings, colored in their theme colors. Thanks to this, they are able to use a powerful version of Five Explosion to defeat Shadow and free the Pinkies she took. Milk claims they are Super Pretty Cure, though it is unknown if this is just something she calls them, or if it is a name mentioned in the legends.

Etymology
Natsuki (夏木): Natsu (夏) translates to summer, most likely referring to her fire-based powers since summer is the hottest of the four seasons, and ki (木) translates to tree.

Rin (りん): A name with many possible meanings, as both a name and a word used in everyday language, depending on how it is written in kanji. Rin's name is written in hiragana instead, so it is not possible to find an exact meaning for her name, particularly since none of the potential meanings relate to her powers or her personality. It is possible that her name was simply an arbitrary choice.

Cure Rouge: Rouge is the French word for red, her signature color. French is also a language often used in the ''Yes! Pretty Cure 5'' seasons.

Trivia

 * At the end of the two seasons, Rin is the only one who does not have any strong bond with any mascot.
 * Natsuki Rin has similarities to the two main Cures of Futari wa Pretty Cure and Futari wa Pretty Cure Splash Star, Misumi Nagisa and Hyuuga Saki, as she is a star athlete in many games. It is therefore strange to see how her relationship with Minazuki Karen, as the latter resembles Yukishiro Honoka, Nagisa's best friend.
 * Rin and Karen's awkward relationship is symbolized by their Cure forms; Cure Rouge and Cure Aqua respectively control fire and water, which are frequently depicted in fiction as opposing each other. Also, as Urara points out in the same episode, the two also represent passion and intelligence, and therefore emotion and logic, another well-established conflict.
 * Coincidentally, the fourth member of Pretty Cure in Fresh Pretty Cure! is named Cure Passion, and has the same theme color as Cure Rouge, who is the Cure of Passion. However, Cure Passion's name is from the fruit passion, and not from the emotion.