Haven't we met somewhere?

I'm introducing the main character.

Park Ji-hoon - He suffers from depression. Because of his depression, he has been unable to make friends. He is an office worker. He later begins dating Park Yeo-joo. He is 22 years old.

Park Yeo-ju was a childhood friend of Park Ji-hoon. Ji-hoon doesn't remember her, so she tries to make him remember her. She suffers from frequent headaches. She's an office worker. She's 22 years old.

Yoon Ji-sung and Park Ji-hoon are seniors at their companies. They are always there to help Park Ji-hoon whenever he's having a hard time. They were set up on a blind date because their parents are close. They are against Yeo-ju and Ji-hoon dating. 27 years old.