Looking for a True Fiancée [指輪をはめたい]

A three-timing 29 year-old man loses part of his memory after taking a nasty fall at a skating rink. The man, who works as pharmaceutical salesman, then discovers an engagement ring in his briefcase. Later, he comes across three different women who all claim to be his girlfriend. To figure out which of the women he planned to marry, he sets up dates with each of them.