Ate ng Ate ko.

A party-loving Yumi is always in conflict with her strict older sister, Ate Riki. As orphans in their young ages, they have always been at odds with each other, until an attack leads to Riki into regressing into a 9-year old version of herself. Yumi now has to take care of the "9-year-old" Riki, and now becomes the "Ate" in the relationship.