Boi, a girl who's living alone now that her father was imprisoned for murder, is penniless and unemployed. Then her father tells her that a rich friend of his wants to take care of her...?

From Entropy:
Saerim Lee gets into an accident and loses her memory as a result. When she goes to school, she realizes that everyone is afraid of her, even her two best friends, who tell her that she was a very mean girl who blackmailed people, using their secrets against them. But she realizes that she can order people around because she supposedly knows these secrets, all of which were forgotten in the car crash. She only has one connection to the person she was in the past, and that is her diary. In it, she wrote of the person she was in love with, but never his name. She will stop at nothing to discover his identity!

A 28-year-old female prosecutor Min-seo is just about to go out with Jun-hyun, a good looking prosecutor whom she has had a crush on since high school. With a successful career and her soon-to-be boyfriend, it seems like she is the happiest woman in the world. However, she suddenly time travels to her high school life while she is chasing a male suspect named Sang-woo; he was a senior in her high school. She genuinely does not want to revive her high school life because it was just the stereotype of a nerd. With a strict moral code as a prosecutor, a teenager’s appearance, and two attractive men, namely Jun-hyun and Sang-woo, around her, her second high school life will be nothing like her previous one.

From Yen Press:

It was love at first sight. The moment Hee-So's eyes met Won-Jun’s she knew it was meant to be. Their relationship took off when Hee-So confessed her feelings on national TV, but less than a month later, Won-jun is ready to call it quits without any explanation at all. Hee-So’s had a lot of boyfriends — Won-Jun is number twelve — but being dumped is never easy. She’s not ready to move on to the thirteenth boy just yet. Determined to reunite with Won-Jun, Hee-So’s on a mission to win over her destined love once more.

The story of two best friends -- a girl who's convinced that she's a lesbian because of her "non-girly" tastes and a guy who believes he's gay because of his feminine personality, and their search for love.

Two high school girls are complete enemies, and they both are in their own gangs. They fight each other all the time, and to get even with the other, one girl tries to kidnap the other's boyfriend. But the information her right-hand girl gives her is wrong, and they kidnap some really good-looking guy who is NOT the boyfriend of the other girl. You know what happens. They fall in love.

Side story: Photogenic
Photogenic centers around the girl in question, who has gone to cram school every day of her school life, finds a photo of an amazingly cute guy, and imagines what it would be like to be his girlfriend, instead of being one of the smartest girls in Korea.

From Springtime Scans:

Woo-jin is headed home for a memorial service. Da-hong is searching the countryside for someone she used to know. Their paths cross when Woo-jin ruins Da-hong's fruit basket (which she had bought as a gift) by accident, and ends up taking her to her destination in his car as an apology. Unexpectedly, the place Da-hong has been searching for is Woo-jin's own home?! What is their relationship to each other...?