|Season||Jewel Star Pretty Cure|
|Birthday Date||September 15|
|Hair Color||Navy (Nanami)
Light Blue (Sapphire)
|Eye Color||Dark Blue (Nanami)
Light Blue (Sapphire)
|Home Place||Takayama Town|
|Relatives||Hosotera Mizuki (mother)
Hosotera Seiji (father)
|Alter Ego||Cure Sapphire|
Nanami has navy coloured hair that she keeps down and some strands tied up into ponytails. Her casual outfit consists of a light blue long-sleeved dress which has a dark blue ribbon around the waist. She wears dark strap on shoes with white ankle socks. (When reading or studying, she wears glasses).
As Cure Sapphire, her hair grows longer and turns light blue while her bands securing her ponytail turn into little bows with golden heart-shaped clip. Her eyes also go light blue. Her dress consists of a....
Nanami is a second year at Takayama Public Middle School who partcipates in fashion and sports club. She likes to read fantasy books and also non-fiction but doesn't read them a lot. She is mostly very quiet and avoids big crowds but like to hang around Akari since she likes her personality a lot. Besides being smart and very quiet, she is sporty and will do anything to help her teammates get over a lost or celebrate with them when they win a game. She plays hockey with Miyashiba Chiyo in the same club.
In Episode 2, she notices that Akari has three stuffed animals following her too school and wonders if they are toys with cameras in them and some of the local boys are seeing what she does in her free time.
In Episode 3, Nanami is practicing for her big Hockey match on the weekend and is having a lot of trouble trying to consentrate since she has a high temperture and decided not to stay in bed. The next day, while doing a practice game with her team, she faints from the high temperture, and wakes up in the nurse office with the nurse, Satoko-sensei and Akari staring down on her. She tries to get out of bed but is pushed back down by Satoko-sensei and is told she has a fever and she must rest and her parents are coming to pick her up. While Nanami is in the back of her dad's car, she notices a girl in red fighting a monster not so far away. And when she gets to the bridge that takes her to her home, the girl is seen flying backwards fast and smashes into one of the poles and slides down into the water. Nanami shrieks and opens the door while the car is still driving and jumps out and runs to the railing to see if the girl has came back to the surface, but sees no figure coming back up. She notices the same mascots on the railing beside her speaking and she freaks out and tumbles over the railing of the bridge. While she falls, a Shiny Bracelet and a blue Jewel Shards appears and helps Nanami tranform into Cure Sapphire and dives into the water and rescues the girl who turns out to be Akari. Cure Sapphire defeats the Kuroppoi with Jet Stream and takes Akari to the hospital.
- Nagahashi Akari - Nanami is Akari's best friend who rescued her from drowning in Episode 3. She gets along with her very well and looks out for her while Akari does the same back.
- Stone - She gets along well with Stone and is happy to let him stay at her place. She thinks of him like an older brother.
"The Cool Stream of Water That Fills the Earth With Liquid, Cure Sapphire!"
"Kūru ekitai to chikyū o ume mizu no nagare, Kyua Safaia"
Cure Sapphire (キュア サファイア Kyua Safaia) is Nanami's Pretty Cure alter ego. Her theme colour is blue and she uses the power of water to defeat Dark Star. When not using her attacks, she is mostly punching the enemy to get them of their feet. She says "Water" before making her move (e.g Water Punch).
Jet Stream (ジェット ストリーム Jetto Sutorīmu) is Cure Sapphire main purification attack. She gathers all her energy towards her palms and face's them upwards towards the sky then yells the incantation then faces her palms towards the enemy, making a stream of water go towards the enemy, purifying it.
Water Punch (ウォーター パンチ U~ōtā Panchi) is Cure Sapphire's more powerful punch. She just punches the enemy and yells out the incantation while punching.
Shiny Cure Sapphire
Shiny Cure Sapphire (シャイニー キュア サファイア Shainī Kyua Safaia) is the form Cure Sapphire is granted by the help of the Faithful Tiara. She is granted the form with the others, beside Cure Ruby, in Episode 37 and can use the attack, Shiny Jewel Blast.