Teru is left all alone when her brother died with only the cell phone her brother gave her to keep her company. It is with this cell phone that she discovers the friend her brother left her in the one that calls himself DAISY. Teru's feelings for DAISY become that of a brothers as he is always there in the shadows, protecting and encouraging her through messages and sometimes physical acts (i.e. throwing tennis balls at bullies from afar, hacking the school computer system at her request), however their relationship has never gone beyond the bounds of Instant Messaging. At the beginning of the manga she is being bullied by the student council and after being maliciously drenched with a hose a mysterious ball flies onto the scene scaring the bullies off. As she tries to return the ball she accidentally throws it through a school window. This results in her meeting with the school Janitor, Tasuku Kurosaki, who demands payment for the window, however hearing Teru is financially incapable of paying for the window he makes her work it off, making her his "Slave" getting her to do his janitorial duties in his place. As the manga progresses, Teru's once negative feelings towards Kurosaki grow into something more romantic. However her suspicion grows that Kurosaki is in fact her beloved ally DAISY and that the phone her brother left her might be more than it appears.