A lonely man living on his own, 25-year-old Song Juhyun.

Just like any other day, he finished his part-time job and returned home.

But… a tiny little kid somehow rolled into his life?

“Umm… Oppa?”

A five-year-old who can barely even say “oppa”!

And that’s not all.

“Oppa, this is BANG!”

With her tiny fingers, she made a gun shape and went:

Bang! Bang!—shooting imaginary bullets in the air.

“How’s that? Cool, right? Oppa, Yoonseul will protect you!”

For her age, she’s surprisingly wild.

A little sister determined to protect her big brother with all her might.

Song Juhyun, wanting to somehow take care of her, started a new venture: the food business.

But then…

“Thanks to Yoonseul, business is even better…?”

[Congratulations. The brother and sister who became the Sun and Moon cheer for the bonds of the new family.]
[Grants talents.]
Suddenly, a legendary figure comes to help the siblings?!

A tough, confident, utterly adorable little sister, Jang Yoonseul,

and a big brother, Song Juhyun, made up of 70% sensitivity and 30% madness.