"Calla" is a 1999 Korean romantic drama that deals with secret admirers, fate, mistaken identities, and second chances. It's a nicely constructed film that begins with an enigmatic tragedy and then jumps back (using the time-honored, mystical 'travel back in time' plot device) to give the protagonist the opportunity to discover the facts behind it, to (perhaps) change the outcome, and maybe even to find love.
The film is enjoyable and well made. If you enjoy the low-key pleasures of Korean TV dramas, you'll find it rewarding. The back story isn't particularly cerebral or deep, but the cast (led by the Song Seung-Heon, the popular lead actor from "Autumn Story") does a nice job, and there are a couple of plot turns that keep it interesting. Sure, there are a some moments that require suspension of disbelief (in addition to the obvious time travel bit, one wonders for example why the Seoul police would respond to a knife-wielding miscreant with 40 officers brandishing assault weapons). But on the whole, it's an attractively filmed drama.
A fancy goods designer, Seon-Woo gets on a bus for his office as usual. In the packed bus he finds Gee-Hee and is captivated by her at first sight. After many twists and turns, he finally makes a promise with her to meet on Christmas Eve. When he gets the appointed spot, he witnesses Gee-Hee held in hostage by a man. The murderer kills her. She's gone. Three years later Seon-Woo prepares to be married to a woman as if he forgot Gee-Hee completely. He recollects his old memory on Gee-Hee at the bus station where he finds her for the first time. He craves her, and suddenly feels strange when he turns back. Something surrounding him is changed but not unfamiliar to him.
His fervent desire retroacts time. He is located on the very Christmas Eve he made a promise with her. Given time is exactly 24 hours. He rushes to rescue her. Can he save her?