After the mourning and grief of Tish'a B'Av, 6 days later the Jewish people celebrate the most joyous day of their Calendar. Tu B’Av is like our Valentine's Day in Israel and is both an ancient and modern holiday. A day of joy, it marked the beginning of the grape harvest in ancient Israel and served as a matchmaking day for unmarried women in the Second Temple period (Jesus time - before the fall of Jerusalem in 70 C.E.). It is still said to be an auspicious day for weddings.
On Yom Kippur and Tu B'Av, the unmarried girls of Jerusalem dressed in white garments and went out to dance in the vineyards. The Mishna says they called to the boys to select one of them. The Talmud states that these were the unmarried girls and boys.
The earliest record of the event is in the Bible, but a bit sad. The tribe of Benjamin had nearly been wiped out by a war, there were only 600 men left and no women or children. The other tribes could not give them wives due to a oath, so the elders told them: On Tu B’Av (a festival of God) “Go and hide in the vineyards. Stay alert — when you see the Shiloh girls come out to dance the dances, run out of the vineyards, grab one of the Shiloh girls for your wife, and then hightail it back to the country of Benjamin. We will sort it out with the parents of the girls.
Kidnapping a wife, the right thing to do? They didn't actually ask God and there was no King, no police. The romance maybe came after the kidnapping and before the wedding. I think once caught the girls would have been given time to get used to the idea before the weddings. A forced wife is not a happy wife and you want a happy wife. It kind of reminds me of an old musical "Seven Brides for Seven Brothers. But in later years the link with romance and vineyards is clear in other Bible verses like the Song of Solomon.