Kyosuke Hibiki is a music teacher who has recently awakened from a coma after having been in a car accident. Upon awakening, he discovers that he is experiencing auditory and visual hallucinations in the form of music and musical notation that appears to surround people. No one is able to find out the source of the hallucinations, and Kyosuke is eventually discharged from the hospital.
Shortly after leaving the hospital, he is accosted by a strange foreign girl named Tena Fortissian, who is a “tuner,” someone with the magical ability to “tune” soul scores. These soul scores come from every living thing and it is the tuners job to make sure that all the soul scores are in tune. Apparently, some “viral” notes have gotten loose and she has been dispatched with a number of other tuners to retrieve the bad notes. To make things more interesting, there is some kind of contest going on to see who can gather the most viral notes.
We also learn that Tena has some fairly severe issues about becoming the very best tuner out there. Most tuners come from families that have been raising tuners for generations. It seems that Tena is a scholarship student who was accepted based on her talent. She has apparently had to put up with bullying from “old money” students who didn’t think very much of her background, which has given her a chip on her shoulder roughly the size of Mount Everest.
It turns out that Kyosuke has become infected with these notes, which have become fused with his soul score. They are most likely the reason why he can now see and hear soul scores. Unfortunately, Tena cannot remove the viral notes without killing him, so she decides to keep him. Kyosuke is extremely not happy with this idea, but Tena somehow rolls right over his protests, moving herself into his house and causing his students to quit school immediately. (Because they decide that he’s a pervert.) She also takes over his bedroom, leaving him to sleep on the floor in the kitchen, and bosses him around continuously.
Despite the bossing around and complete home invasion, Kyosuke slowly grows to appreciate Tena for her musical ability (even if she is incredibly bossy and arrogant). In turn, Tena grows to respect Kyosuke somewhat, though she never lets up on the continuous bossing around. Tena is able to charm and befriend Kyosuke’s former students, and they decide to come back and have him be their teacher. (They put up with Tena’s bossiness and arrogance because they believe that she is a cute and adorable ten year old, not a fifteen year old who acts like a ten year old.)
Of course, the situation becomes increasingly complicated when two other tuners discover Kyosuke and his anomalous soul score. Mezzo and Sopra decide to steal him, only to encounter Tena who is less than happy about her “servant” being harmed. After a battle that leaves Tena without her unmentionables, they carry off Kyosuke and subject him to various scientific experiments. These two are researchers who are studying soul scores. They are particularly interested in the viral note that has become fused to his soul score since viral notes usually result in the infected person becoming some kind of monster. In Kyosuke’s case, it appears that the viral note has integrated into his soul score seamlessly, without causing any damage. They are very curious, and want to find out what happened.
Then Tena turns up and a fight ensues. Kyosuke manages to end the fight, though he takes some damage. Kyosuke suggests an arrangement where they all essentially “share” him. (Mezzo and Sopra can experiment on him, and Tena can use him as her tracker.) Somehow “sharing” is interpreted as “Mezzo and Sopra move in with Tena and Kyosuke” which causes Kyosuke some aggravation.
Volume one closes on two new tuners; Arun and Duon. This is a fairly good indication we might see them in the next volume.