Ringo is a kind, studious girl who wears thick glasses, always there to support Ikki since they were young. She started out with a sisterly affection for Ikki, which eventually progressed to infatuation and eventually deep love, which she still tries to deny though it is clear to everyone except perhaps Ikki himself. Ringo has always let Ikki do things as he liked, turning an eye away during his gangster era as the leader of Eastside 'Undefeatable Babyface'. She is a pushover, her friends Emily and Yayoi easily manipulating her to doing things for them, and the teachers always picking on her rather than Ikki and gang. However, as a Storm Rider she is more strong-willed as a person, and punishes the Skull Saders, who attacked Ikki, with the other members of the Noyamano household, for misusing ATs.
Ringo, encumbered by her duty as the leader of the Sleeping Forest, is put in a difficult position, due to the power struggle between Sleeping Forest, who seeks to protect the Sky Regalia, and Genesis, who seeks to take the Sky Regalia. She was put in a dilemma when Ikki was given reign over Genesis; since that directly made him her enemy. Ikki taking over Genesis caused Sleeping Forest to respond in kind, attacking and paralyzing Simca, who had recruited Ikki, waistdown. Ringo led the attack as the true successor of the Sleeping Forest, 'Crazy Apple'.
'Crazy Apple' was eventually fully brought out when Ikki learns the truth behind Simca's attack, followed shortly by Ringo's unwanted kiss with her tuner Kanon. After realizing that Ikki had reached a level of riding where he was a serious threat to Sleeping Forest, she put herself in battle with a serious Ikki, and decided to crush him and remove him forcibly from the world of ATs, so that he would not die by getting caught in between.
The Ringo when she is 'Crazy Apple' seems to be an entirely different person, taunting, cold, and ferocious in her attacks. She mocks Ikki for his little tricks and doesn't hold back in all her attacks, even releasing the Thorn Regalia with the intention of taking Ikki down. She destroyed Ikki's Infinity Atmosphere because he was armed with the fake Wind Regalia, though she took equal damage in return. Her infinity atmosphere is called " 'Infinite Chain' Turquoise Sonia"
Eventually Ikki came to understand Ringo to a level where words were not needed and after Ringo fell, exhausted from the race, he picks her up and told her he forgives her and thanked her for going easy on Simca. He then finished the race with a draw, carrying Ringo all the way to the end point of the race. Ringo later learns that Ikki was going to leave the Noyamano household to pursue his own path (and to prevent a recurrence of such events) and Ringo acknowledges his path and let him 'go outside his cage to find his wings'. Before he left, Ringo finally confessed to Ikki.
Just before the battle against Genesis, Sora reveals a captive Rika and is trying to force the team to give up their advantage in the forest. Ringo, as leader, decides to abandon Rika in favor of keeping their advantage. This puts her at odds with Mikan, who believes they should go rescue their sister.
When Mikan decides to go help out Rika despite knowing that her life is in considerable danger, Ringo forces Mikan to duel with her in order for Mikan to leave to help Rika, because Mikan would face certain death if she went against Genesis alone.
Ikki, eavesdropping on their conversation, decides to help them out by going out himself to save Rika. This reinforces Ringo's love for Ikki and she realizes that Ikki has always been there for her in her time of need. In the moment for the tuning of Ikki's regalia, with Kururu unable do to it, Ikki chose her to do it because she's the girl that always be by his side and the only one that really knows him in that way she became Ikki's Link Tuner.