The long-term sluggishness of Japan's economy has made cheap dates, emphasizing fun and togetherness over glamor and extravagance, quite common, even popular.
A picnic in the park is considered quite romantic, especially in spring. Beyond displaying your vocal talent (or lack of), the willingness to stand center-stage (in a private karaoke box) and possibly make a fool of yourself proves you are not too proud, a trait respected in Japanese society.
Plenty of courses are served, but never in a multiple of four because the number four sounds like the word for death.
Additionally, the different foods served all have special meanings, for example lobster might be served because red is a lucky color or clams served with both shells symbolize the couple’s union.
In general, avoid drawing attention to yourself or your date (no PDA's).