Located on the southeastern tip of the Korean Peninsula, Haeundae-gu of the city Busan draws one million visitors to its beaches every year. Several years ago, Man-sik, a Haeundae local, lost Yeon-hee's father due to his mistake in the 2004 Indian Ocean Earthquake while deep-sea fishing together at the Indian Ocean. Because of this, for years, Man-sik wasn't able to become involved with Yeon-hee, who runs an unlicensed seafood restaurant, despite her attempts to start a relationship (Yeon-hee doesn't know that her father was killed due to Man-sik's mistake.

Dong-choon, another Haeundae local and also a neighbor of Man-sik, teams up with Man-sik's son and gets involved with some 'illegal' activity to earn money, but the two end up getting caught by the police. Afterwards, Dong-choon's mother, concerned about her unemployed son, decides to prepare him for a job interview, but Dong-choon refuses. As time pass, Man-sik finally plans to propose to Yeon-hee on a night with fireworks.

Geologist Kim Hwi somehow runs into his divorced wife, Yoo-jin, who is preparing for an expo in Busan. Although Yoo-jin has a daughter (and also a new boyfriend), they decide not to tell their daughter that he (Hwi) is her real father, afraid that the child would be greatly shocked.
A wealthy college student from Seoul, Hee-mi, accidentally falls into the ocean from a luxurious yacht. Hyeong-sik, Man-sik's younger brother and also a lifeguard, rescues Hee-mi rather 'violently'. Hee-mi becomes greatly angered by the 'violent' rescue and annoys him by following him around. But as time passes on, love starts to grow between them.