The Ultimate Vow, Unknown to You

Stuntman Cha Dal-geon gets involved in a tragic airplane crash and ends up discovering a national corruption scandal in the process. Go Hae-ri, the oldest daughter of a deceased marine, decides to work for the National Intelligence Service as a secret ops agent in order to support her mom and younger siblings, although all she wanted to do is to become a civil servant.

Kisaragi Amatsuyu is invited out alone by the cool beauty upperclassman Cosmos and his childhood friend Himawari. Expecting to hear their confessions, he triumphantly goes to meet each of them in turn. But Cosmos and Himawari both instead confess to Amatsuyu that they like his friend. Amatsuyu fights this lonely battle, but there is another girl who is looking at him. She is a gloomy girl with glasses and braids. Amatsuyu finds that he hates her, because she's always turning her sharp tongue only on him and finding enjoyment in his troubles. But it turns out that she's the only one who actually does like him.

Haru Satonaka is the captain of an ice-hockey team, a star athlete who stakes everything on hockey but can only consider love as a game. Aki Murase is a woman who has been waiting for her lover who went abroad two years ago. These two persons start a relationship while frankly admitting to each other that it is only a love game. …The result is the unfolding of a drama of people with their respective pasts and with their pride as individuals.

Dongbaek is a single mother. When a potential new love enters her life, she finds ways to defy the social stigmas surrounding her.