When his boss, Dae Jung, goes missing in a ship accident, the company sends Woo Joo to Osaka to finish his business. On his last day in the city, Woo Joo chases someone looking exactly like Dae Jung to Taisho, an area in Osaka. He ends up losing him, but the sound of a guitar draws Woo Joo to a small bar, Pier 34. Its owner, Snow, somehow reminds him of Dae Jung, and listening to his music brings back memories. After passing out right there, Woo Joo ends up missing his flight back to Korea. He quits his job on a whim and soon meets Haruna, who is learning how to play the guitar from Snow. Woo Joo decides to stay at Pier 34 until he finds Dae Jung and so begins an unlikely vacation for him.
Aoi studies photography at a school in Tokyo. She undergoes a heart transplant operation and goes to the island of Okinawa to recover. Her uncle lives on the island. There, she holds a camera and walks along the island. Aoi hears the sound of a trumpet. She looks up and sees a young man playing the trumpet. His name is Ji Oh.
Mika goes all the way to Seoul to see her sweetheart Hyeong Jun who's been waiting for her. She suffers faints at the airport and she mistakes Kim Gyeon as Hyeong Jun due to trauma. Kim Gyeon also ends up falling in love with her, thus disrupting the balance between the three. Their memories start intertwining, but, before long, a tragedy occurs.
Emilia, a Filipino who arrived in Japan with aspirations of becoming a model, coincidentally encounters Matsuyama Mirai, an aspiring photographer. Their connection deepens as they find themselves drawn to each other. Mirai, intent on immortalising their moments together, diligently captures their essence through the lens of his camera. However, an unexpected parting disrupts the flow of their narrative. Subsequently, the saga of these two individuals unfolds beyond the shores of Japan, traversing the vast sea to the Philippines, where their story takes on new dimensions.
One Sunny Day "OSD" gives the same light heart-fluttering vibes with 2 strangers having to spend a few days together on Jeju Island and unexpectedly find themselves to be attracted to each other at parting, being tentative of their new feelings, and longing after sorting out their emotions. OSD has the added bonus of several scenic sites on Jeju Island as backdrop.
