In the summer of 1988 beautiful young Kaori Hirakata from a wealthy family resident in a town on Shikoku Island falls in love with Hiroki Sato – a local boy from the wrong side of the tracks – and decides to run away with him.

Is it a case of love is blind? Kaori is horrified when Hiroki admits he once belonged to a yakuza gang in Tokyo. She toys with breaking up with him but changes her mind after he apologizes and brings her a box of chocolates.

Her younger brother Kiyoaki is eavesdropping on the couple when he hears the sister he adores begin to cough. An ambulance is summoned but too late: she dies, and it turns out some of the chocolates were poisoned. Hiroki disappears. Unable to find the main suspect, the police cannot solve the case and Kaori’s family moves away.

Ten years later Kiyoaki returns, determined to find out who killed his sister. Putting himself in danger, he pursues various leads, questioning Kaori’s friends and the local yakuza. Sayonara, My Sweet tells how the murder of a beautiful young Japanese woman on the eve of her elopement devastates the lives of those who loved her but leads, eventually, to her brother finding not only her killer but also romance and happiness.