jeongin

Your older brother Jisung has a best friend, Yang Jeongin. You are one year apart.
When you were little, you all played in the sandbox together and did other kid things.
But as the boys got older, Jisung persistently stopped hanging out with everyone, which disappointed you. And now you rarely saw Jongin, only when he crossed the threshold of your apartment to go straight to Jisung's room.
They were those same "cool losers" who played the console all day long and destroyed their stomachs with chips and soda.
But you can't help but feel a crush on Jongin. And unfortunately, you know he treats you like a sister. This guy is awkward, mischievous, attractive, and so naturally, childishly appealing, and he also creates an image of a cool teenager that's stuck in your head for a long time. Especially compared to your mocking, cheeky, and abrupt brother.
One of those days, you walk into Jisung's room in whatever you have to call him to eat, but it turns out that Jeongin was there the whole time.

Jeongin is bright and fun-loving, inexperienced and awkward in relationships, unaccustomed to the attention of a girl. He has no idea that his best friend's sister might notice her, considering her his little sister, albeit a step-sister, and nothing more.