After Nam (Louis Koo) and Mi (Rene Liu) agree to break off their relationship, Mi still receives short messages from Nam during her birthday. However, one year, the messages stop; and she later finds out that Nam had died a long time ago; and all the messages had been sent by her sister in his name all this while.

Birthday wishes are something we look forward to every year. The same goes for Nam (Louis Koo) and Mimi (Rene Liu), who first met at a party and got attracted to each other. However, the last birthday message that Mimi received from Nam is delayed for 42 hours.

In "Happy Birthday", Nam, a student from the University of Hong Kong, has many girlfriends but none of them lasts because his heart is still with Mimi. Mimi knows about Nam's feelings, but she is afraid losing Nam - just as she did her mother who left her when she was a little girl. Therefore, she suggests that they both remain best friends instead of as a couple as she believes that not having each other is the best way to keep a romantic relationship.

The story continues with Nam and Mimi in their on-off relationship. One day, Nam finally announces that he would be getting married to someone unknown to Mimi. Devastated, Mimi accepts her fate, taking solace in the fact that she would still receive birthday wishes from Nam every year.

On the whole, the movie is a compilation of a few different scenes: the "sad" ones where Nam drops by at Mimi's house to bid her farewell; the "happy" ones where Nam sends text messages to Mimi when her house in Japan has no electricity due to an earthquake and the "romantic" ones include a scene when she packs him lunch and he eats it even though he is full.

The two leading stars are credible in their performance. However, Rene is a little too old for her role - making it seem as if Nam and Mimi are siblings rather than lovers. The flow of the story at the beginning is slow - especially at scenes where there is no conversation for about 30 seconds. Moreover, the storyline somehow is too cliche, which didn't help matters.

"Happy Birthday" is a sad romantic drama about two lovers who cannot be with each other. Those watching it should remember to bring along a packet of tissues. Just in case.

In this story loosely based on Rene Liu's own short story of the same title in her book I Want Go With You, this birthday wish is of great importance to student Mimi (Liu).

"Happy Birthday" tells a story of a young university couple, Mimi and Nam (Koo). A simple gathering among friends sparked off their relationship. Mimi, a music major whose wish is to be a pianist with hopes of moving on to Vienna, meets Nam, a student in Hong Kong University.

Nam, who has always been surrounded by girls, is one who is of full confidence of himself, while Mimi, whose mother had left her when she was at a tender age, is the opposite, as she has no confidence in herself.

This difference becomes a reason for the turning point in their relationship when Mimi chooses to stay as 'more than good friends' with Nam in fear of losing him. With this begins their on-and-off relationship, or is it that they have never really broken off? This situation continues on, from the day Nam leaves to further his studies, and Mimi going off for the same purpose.

In all these years apart, Nam never fails to send Mimi a simple 'Happy Birthday' greeting every 6 June, her birthday. With one girl after another in his life, this is still something he never fails to do, and this is also the one thing that Mimi looks forward to yearly. A few years after telling Mimi that he is getting married, Nam fails to send her a birthday greeting on time, as it is being delayed 42 hours. This is due to a heart-rending event which Mimi will never get to know.

Director Jingle Ma once again proves his directing skills through this touching story. First time on-screen couple, Koo and Liu do a good job, creating a fresh on-screen chemistry.

The plot is simple and straight-forward, making it predictable for some happenings. This kills the story at some point, but thanks to a few heartfelt scenes, such as when Nam comes to bid farewell before leaving, the sms-es between them when Liu is faced with a blackout alone in Japan or the time when he declares his marriage to her, the movie is saved.

The beginning of the movie, introducing their relationship, is rather slow, making it a bit boring. At the very moment when you think you are about to fall asleep, grief comes into the picture, along with different emotions to the characters. The huge boo-boo is the dubbing on Liu's part (as Liu is Mandarin-speaking), which for few scenes, decreases the sad and heart-gripping element.

"Happy Birthday" is a whole one hour 45 minutes of love story to warm your heart, with a belief that true love leaves an eternal hope.