|u m i r y u u z a k i|
★ S T O R Y & B A C K G R O U N D ;
Umi is introduced to the series as the only child of a very wealthy couple. She attends a private school meant for daughters of politicians and businessmen. During the visit to Tokyo Tower that signals the beginning of the series she stands out before Hikaru's schoolmates because of her looks and overall snobby appearance. In fact, she seems quite self-centered and arrogant during her first exchanges with Hikaru and Fuu. However, with time, this turns out to be just a front to hide a truly caring nature.
During aforementioned field trip to Tokyo Tower she's swept into another world called Cephiro along with Fuu and Hikaru: two girls from different schools. Upon arrival, a magician (or "guru") named Clef informs them that in order to return home they must become the legendary Magic Knights who will rescue Cephiro's Pillar, Princess Emeraude, from captivity at High Priest Zagato's hands. Cephiro happens to be a magical land where sheer will becomes power: just like the Pillar's will sustains the whole world, the three girls' determination will help them gain stronger magical powers and so fulfill their quest as Knights. Extremely annoyed and put off by the strangeness of the situation Umi first refuses the mission. She seems more concerned with getting back home because she has an important fencing match to attend. She takes the situation rather lightly, seemingly uncaring that Cephiro's destiny is at stake. In the end she has no choice but to accept because she wants out of there.
After a series of trials that makes the three girls become fast friends Umi finally accepts the true importance of fulfilling her destiny and becoming a Magic Knight. The journey to achieve this makes her grow up emotionally and become less selfish and more eager to open her heart to others. At a point when one of Zagato's minions, Alcyone, wounds her severely, Umi still risks her life to save Hikaru and obtains her water magic from Clef in the process. After retrieving the legendary mineral Escudo from the Fountain of Eterna, her will helps her make the sword made for her with it evolve as her heart matures. Fuu and Hikaru became the most important persons in her life, for whom she cares to a sisterly level. She is the first to awake her emblem Mashin (or Rune God) at the temple of the sea: the water dragon Celes.
Celes demands a proof of the strength of her heart in order to recognize her as a true Magic Knight worthy of donning his powers. Umi proves herself by not abandoning Hikaru and Fuu when another of Zagato's servants, a child capable of summoning beasts named Ascot, attacks her friends while they wait for her. Not only does Umi defeat Ascot, but makes the little boy see his mistake: by serving Zagato he is endangering and badnaming his monster friends by making them fight on his behalf. Ascot understands this and apologizes to Umi, who forgives him. Considering this plenty of proof of Umi's strength of heart, Celes reveals his true form and accepts Umi as his Knight.
In the end, after the three Mashins are awoken and Hikaru, Umi and Fuu indeed become the legendary Magic Knights, they confront and defeat Zagato only to discover Princess Emeraude is actually in love with him. By thinking only about him Emeraude's prayers are faltering and affecting Cephiro's balance. So to grant her only selfish wish and save the world from destruction the Princess summoned the three girls to become the Magic Knights from the legend. After Zagato dies a darker personality takes over Emeraude's will and she attacks Umi and the girls. Emeraude's true self manages to resurface and asks them to kill her so she can be with Zagato forever. After much hesitation and unwillingness from their part, the Magic Knights understand this is the very reason why they were summoned to Cephiro and fulfill the Princess wish by killing her.
Once their tragic mission is accomplished the three friends return to Tokyo to discover time stood still in their absence. The need to slay both the Pillar of Cephiro and her lover leaves a great deal of guilt in their hearts. Unable to move on and determined to do something positive for Cephiro and all the people they met in their journey, the girls gather at Tokyo Tower and return to the magical world without knowing who or what has summoned them there. There they help saving Cephiro from destruction born out of the fear of its inhabitants' hearts, now Pillarless, and defend it from the invasion of its neighboring countries now its barriers are weakened.
In the end the three of them decide to fight for Cephiro again by their own free will. Umi proves how much her time in Cephiro has changed her by expressing her own desire to protect all the people they met during their previous time there and stands by Hikaru and Fuu in their decision to search for a new Pillar so Cephiro can become stable again. The new Pillar is meant to be chosen out of the strongest hearts present in Cephiro: the final trial turns out to be between one of the invaders, Eagle from Autozam, and Hikaru herself. Hikaru wins but refuses to abandon Eagle, who, having failed the test, is bound to disappear.
Mokona, the creator of Cephiro's universe and Earth, is moved by the friendship and strong will of the Magic Knights and so allows Umi and Fuu to save Hikaru and bring her back from the trial dimension together with a comatose Eagle. The girls unite their will to grant their wish to establish a new system meant to sustain Cephiro by its people's collective will, not the Pillar's alone. Cephiro is restored and Umi, Hikaru and Fuu remain able to travel back and forth from it after returning to their own world. That way they can visit the many friends they made and witness the birth of a new Cephiro.