Baka Deka Imouto ga Yattekuru!

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's 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!!!

So begins this sibling comedy.

(Source: Kadokawa, translated)