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 has a very straightforward and down-to-earth personality that sharply contrasts with the cheery and optimistic Nozomi Yumehara, 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 "Full Throttle Passion, Cure Rouge!", 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. Sometimes, when Rin runs into some troubles that really frustrate her, she could become hopping mad, especailly with her favorite sports, such as soccer.
Rouge Fire - The red butterfly mark on her arm ingnites on fire and produces a mass of fire. She then thrusts her hand at the mass, sending it to the enemy and defeating it.
Rouge Burning - Red light from Cure Rouge's butterfly bow shines, whereas the light follows her right arm. When it has reached her fingertips, the Rouge Tact appears. Using this, she holds up the tact, then pulls it back. The rod portion of the item ignites on fire, and like her first attack, produces a mass of fire. She then thrusts the tact at the mass, sending it to the enemy and destroying it.
Fire Strike - Cure Rouge makes fists with both hands and crosses them in front of her chest, causing the butterfly-shaped emblem to glow with her signature color. A ball of fire appears in front of Cure Rouge, and she kicks the ball at high speed at the enemy. The enemy gets surrounded by a red butterfly upon impact and is usually defeated.
- Rin is afraid of ghosts, just like Naruto Uzumaki, an anime character voiced by the same voice actress (Takeuchi Junko).
- Rin is the first sporty Cure who is not the leader of the group.
- At the end of the two seasons, Rin is the only one who does not have a strong bond with any mascot.
- Rin is a little bit similar to Nagisa from Futari wa Pretty Cure, in terms of personality. However her relationship with Karen, who resembles Honoka, is slightly awkward. This may be due to their opposite Cure forms; Cure Rouge and Cure Aqua control fire and water respectively, which are frequently depicted as opposites. Also, as Urara points out in the same episode, the two also represent passion and intelligence, another well-established opposite.
- Coincidentally, Cure Passion from Fresh Pretty Cure! has the same theme color as Cure Rouge, who is the Cure of Passion. However, Cure Passion's name comes from the passionfruit.
- Rin is the first Cure who plays soccer, followed by Hibiki from Suite Pretty Cure♪ and Nao from Smile Pretty Cure!.
- Cure Rouge is the first Cure to have red as their theme color, and is followed by Cure Passion.
- Rin is one of the few Cures to have short hair in her Cure form, along with Cure Black, Cure Pine, Cure Sunny, and possibly Cure Bright (Michiru).
- In the Pretty Cure All Stars Suite Flower Card Collection, Rin is represented by the hibiscus, which symbolizes style and strength in the Language of Flowers.
- Rin is the first Cure to have more than one sibling, along with Nao Midorikawa.
- Rin is the first Cure whose parents own a flower shop, second being Tsubomi Hanasaki from Heartcatch Pretty Cure.
- Cure Rouge is the only Cure with a French name.
- Rin is the first Cure to be from royal/famous descent, as shown in episode 27 of Yes! Pretty Cure 5.
- When Rin transforms into Cure Rouge, her hair is the most noticeble color change (Brown to Red).
- Rin shares her name with a singing program from Vocaloid, Rin Kagamine, Which also ties her in with the Suite Cure`s Melody and Rhythm because there hair bow`s are thought to resemble Rin Kagamine`s.
- Her voice actress Takeuchi Junko played another character with fire element, Kanbara Takuya from Digimon Frontier.
- She is the second sporty Cure to be in love.
- She is the first Cure to have fire powers.
- Rin will appear as Cure Rouge to give the 10th Anniversary Congratulatory Message at the beginning of episode 17 of Happiness Charge Pretty Cure!