Watashi ga Oneechan Nan Dakara ne!  

私がお姉ちゃんなんだからね！

Misora Takatsuki is a 15-year-old freshman at high school who struggles with being short. She's often mistaken for an elementary student and her friends tease her about it, adding to her self-consciousness. Her younger sister Kotori, who is only 11 years old, looks like she should be in high school or even older. Despite this, Kotori loves playing with Misora, but the older sister feels embarrassed by what seems like a reversal of roles in their sibling relationship.