SpoilerThe target the brothers are ordered to watch. She goes to an all-girls school, and has fallen in an obsessive love with Keiju Tabuki, who was Momoka's (her big sister) boyfriend. Her parents divorced as a result of arguments involving that Ringo's birthday is also the date Momoka died, thus leading to fights of whether mourn Momoka's death or celebrate Ringo's birthday.
She possesses a diary that was used by Momoka which foretells future events, and Ringo often goes to great lengths to make sure what is written for each day has been fulfilled, as she believes it is her destiny to become Momoka herself so that she and her parents can be happy again. However while events foretold in the diary do come true, it rarely happens the way Ringo imagines it.