Sumire is the older sister while Lily is the youngest one. Sumire goes to the same school as Minamo and her friends as a third-year middle school student. She got a graceful and mature personality but a bit too single minded on tasks she was given by anyone and do anything to complete them. As Flower Knight Sincere, she prioritizes to gather the energy source, Musessence, over fighting the Princesses in Alicepia, for the White Queen in order to prevent the destruction of the fantasy world.
Lily herself is a 5th grader student and is a quiet girl towards others. But she and her older sister spend time in Alicepia with the mouse Alicepian, Thoma, the three play and hang out together until one day, Thoma, disappeared due to the humans giving him too much Musessence to handle and she was furious to see her friend die despite not her fault. She then later appeared when Sincere lost against the Princesses for a second time and is being scolded by the White Queen. As she reappeared at Flower Knight Purity, the White Queen suggested Sincere take her partner with her for backup during the battles against the Princesses. However, Sincere refuses insisting that they are more than capable enough to take down the Princesses herself. Purity herself was more aggressive and will stop the Princesses from gaining Musessence to prevent more Alicepians dying off.
This is from Episode 35 where the Princesses were trying to stop Purity (Lily) from destroying Alicepia since her heart was too closed and her blades are powerful enough to surpass them. However, Sincere (Sumire) was the only one who stopped Purity's madness. As her older sister, Sumire (who managed to stop her blind rage over the loss of Thoma thanks to Minamo's determination to stop the fighting) conveys her sincere feelings for Lily, melting her icy heart. Thanks to that, Purity managed to stop her rampage, but the White Queen herself appeared to stop the Princesses with a new monster called a Jammersnark. She never cared about Lily and Sumire in the first place and used their hatred to gain enough power to crush them after the two lost their powers. But Thoma appeared again as a Musessence to give the Kazahana sisters one last gift to transform into Princesses Viola and Neige to defeat the monster.
GIFs
