Scarlet Heart: Ryeo was so good, here's a possible synopsis for Part 2: 

A passerby bumps Hae Soo (now Go Ha Jin) as she's working at the cosmetics store. His clothing is disheveled, and his long, unkempt, bleached blond hair partially covers his face. His visible eyebrow is pierced (and maybe his nose or tongue, too). He wears a guitar on his back. Ha Jin is startled but apologizes, saying, "I'm sorry, customer," several times. He rudely replies, "I ain't your customer, pretty girl. And watch where you're going next time." He sneers and stomps away.

Ha Jin THEN turns around and sees a bespectacled professor (the former royal advisor Choi Ji Mong) observing her. Due to her near-drowning, hospitalization, and amnesia, she doesn't remember him. (This fulfills her wish in episode 1 to "forget everything.") Her coworker tells her to go home and rest, but instead, she goes to the Goryeo Era Paintings Exhibit. Dirty Musician sees her there as she's sitting on the floor, crying, after viewing the painting of Wang So standing alone in the courtyard.

Dirty Musician says, "Hey, pretty girl. What? You following me around like a little puppy dog now?”  Ha Jin is visibly frightened. He continues, “Don't worry. Girls like you ain't my type: high-class pretenders who think they know art. What? This makes you cry? You don't understand this stuff at all. You want to see real art? I'll show you real art." He reaches into his filthy coat and throws a crumpled flyer at her. "Here, come to my concert," he says. "I'll show you that my music is the only real art." He walks away, laughing.

She pushes the flyer with her foot, but she later attends the concert with her friend/co-worker. The music is awful, screaming garbage, but they think that another band member, the younger half-brother of Dirty Musician, is cute and talented, and they eventually meet him and form a friendship.  Dirty Musician is poor and mostly homeless, but he gets some financial help from this half-brother, who receives a monthly allowance from their father, who was a farmer.

The farmer father inherited a lot of land from his late wife (Dirty Musician's mother), and with his new wife's greedy encouragement, he turned that land into a real estate empire. She brought her own son to the marriage, and a few years later, insisted that Dirty Musician be sent away to live with his uncle (the dead mother's brother), due to family discord. A few years later, when Dirty Musician was 17, the uncle died. Dirty Musician quit school and started living on the streets and formed a band. Now in his late 20s, Dirty Musician recognizes that he won't achieve success or stardom. He's full of anger, and the chip on his shoulder has made it hard for him to realize his true musical talent and intellectual ability.

Ha Jin enrolls in a class about the history of Korean cosmetology that's taught by the Professor, who is an expert in history, ancient medicine, and astronomy. Gradually, he orchestrates a series of coincidental meetings between Ha Jin and Dirty Musician. Slowly, they become closer, and they research and discover Dirty Musician's lineage and direct bloodline to King Tae Jo of Goryeo.

The Professor is also the person who rescued Ha Jin from the lake and who told her that her life might be changed if she died and came back again.  Because she saved a drowning little boy, her life is now blessed.  Her former boyfriend and "that wench who stole him" also make an appearance somewhere in Part 2, and the former boyfriend (former Prince Wook) tries to win her back.

Ha Jin and Dirty Musician (the former King Wang So, if you hadn't already guessed) finally recognize and accept their history and fate. He receives his rightful inheritance, becomes the manager of his half-brother's successful band, and benevolently allows his older stepbrother to manage the real estate empire for the family. Because of Ha Jin's patience, kindness, and understanding--and with the help and cosmic guidance of the Professor--he has become a new man, the man he was meant to be.  This time, Hae Soo and Wang So get their happy ending.