Baka Deka Imōto ga Yatte Kuru!

I, Kasuka Nagasu, have a sister named Kujira Nagasu who is two years younger than me.

Today is the day I reunite with Kujira for the first time in five years—ever since our parents were transferred overseas. In my mind, she was still that tiny girl from back then...

I hear Kujira calling out my name.
I wonder if she's grown a little...

Wait—
SHE'S TOO BIG!!!!
She's gotten insanely huge!
She's carrying a rolling suitcase like it's a handbag!!!

—And so begins the sibling comedy woven by these two!!!!