IKEWH!: Heartstrings Characters part 1.

Yeah, there's a lot of people in this one.

Let's do the top four characters first.

Derp:
The main female lead is a young university student. I can never remember her name so from now on, she will be called 'Derp'.
She's ditzy, cute and chronically late to class, just like every other female romantic lead in kdrama. (Except for that stuntwoman from Secret Garden.)

God, you were awesome.

She lives with her Grandfather and goes to some sort of performing arts university. Derp is very good at playing traditional Korean instruments.

Sexy Mc HorseFace:

Our romantic male lead is Sexy Mc HorseFace (HorseFace for short) He's also a student at the performing arts school but he sleeps through class because he's a rebel.
HorseFace is the lead guitarist and vocalist in a rock band called 'Stupid'. Shockingly, I didn't make up that name. The band really is called 'Stupid'.
He also seems to like riding bicycles and brooding.

Ballerina and Mr Broadway:

Ballerina teaches dance classes at the university. She has some kind of ankle injury.
Sexy Mc HorseFace has a thing for her.

There's some kind of bad blood between her and Mr Broadway. They probably dated.

Mr Broadway has been out of Korea for a while. Possibly on broadway. His managers have made him come back to Korea. I'm unsure if he's going to teach at the university or not.
He has mad scrapbooking skillz.

Bonus Character

This is Derp's Grandfather. Do not cross him. He will crush you.