-What happened between these two guys??
According to legend, the Milkiy Way, a river of stars that crosses the sky, separates these lovers, and they are allowed to meet only once a year on the seventh day of the seventh lunar month of the lunisolar calendar. The celebration is held at night.
I personally think that this is a kind of sad story...but we celebrate it.
-How to celebrate it??
People generally celebrate this day by writing wishes on tanzaku(短冊), small pieces of paper, and hanging them on bamboo with other decorations.