Tidal Wave

Man-sik is haunted by the 2004 tsunami that claimed Yeon-hee's father while they were at sea. His momentary judgment leads him to withdraw from Yeon-hee and from her uncle Eok-jo, and he carries that guilt for years. The tragedy becomes the emotional backdrop for the rest of the story.

Yeon-hee runs an unlicensed seafood restaurant and longs to start a relationship with Man-sik. She actively pursues him, hoping to bridge the gap created by his past guilt. He remains reluctant, still haunted by what happened years earlier.

Eok-jo, now Busan's head chairman, pushes to designate Haeundae as a special tourist zone. His plans trigger backlash from locals who fear losing their neighborhood. The clash underscores the tension between development and community interests.

Dong-choon, Man-sik's half-brother, teams up with his son Seung-hyun to pursue illegal activities. Their scheme is uncovered by the police, and they are eventually caught. The family’s criminal entanglements contrast with the personal stakes of the coming disaster.

During the fireworks festival, Man-sik plans to propose to Yeon-hee. Yeon-hee signals acceptance by a ribbon hung outside her restaurant the day after, and he looks forward to their future. When he finds no ribbon and learns from Dong-choon what he told Yeon-hee about her father's death, he grows furious and confronts him; a flock of birds suddenly takes to the sky.

Geologist Kim Hwi crosses paths with his ex-wife Yoo-jin and their daughter Ji-min, but they keep their relationship status a secret from Ji-min. They worry about how she might react if she learned Hwi is her biological father. The family dynamics remain emotionally charged before the disaster.

A wealthy Seoul student, Hee-mi, accidentally falls into the sea from a yacht. Lifeguard Hyeong-sik rescues her from the water, but she is angered by the manner of the rescue. Despite this rocky start, she begins to follow him and their relationship starts to form.

Hwi notices the Sea of Japan (East Sea) showing activity similar to what was observed in the Indian Ocean five years earlier. The Disaster Prevention Agency dismisses the risk, leaving people unprepared. A landslide near Japan triggers a megatsunami heading for Busan, giving residents only minutes to react.

Thousands flee when the sea recedes and then returns as a massive wave. The tsunami sweeps through Haeundae and into Busan, destroying buildings and trapping people in the surge. On the Gwangan Bridge, friends and family are carried away by the relentless water.

During the chaos, Eok-jo appears in the streets and helps Man-sik escape the worst of the waves. He sacrifices himself, saving Man-sik but being carried away by the currents. The disaster continues to unfold as the city struggles to endure.

A lighter from a tanker incidentally ignites a petrol leak, triggering an explosion that severs the Gwangan Bridge in half. Shipping containers are hurled into buildings along the shore, creating further chaos for survivors. The bridge collapse marks a devastating turning point in the disaster.

Hyeong-sik jumps from a rescue helicopter to save Hee-mi in the sea. On the rope with Joon-ha, he realizes the rope will break and makes the ultimate sacrifice by cutting the rope so the other can go up. He falls back into the violent water, sacrificing himself to save her.

Yoo-jin is trapped in floods inside an elevator while Ji-min speaks with her on the phone. A rescue worker frees Yoo-jin, and on the rooftop she is reunited with Ji-min and Hwi. Hwi reveals to Ji-min that he is her birth father, and they share a hug before another megatsunami claims them.

A memorial service honors the thousands who died, including Hyeong-sik, Hwi, Yoo-jin, and Eok-jo. People come together to reconstruct Busan, clearing ruins and rebuilding livelihoods. Among the ruins, Man-sik finds the red ribbon, symbolizing Yeon-hee's acceptance of his proposal.

The city remains in ruins, but a hopeful atmosphere pervades as communities begin anew. Man-sik holds onto the red ribbon, reaffirming Yeon-hee's acceptance and their shared future. The final scenes show Haeundae slowly recovering, with a sense of resilience and possibility.