There are around 600 different cherry tree variants across the globe, and one type that flower uniquely are the Yaezakura style. They're also known as double cherry blossoms, and they are more densely packed with petals than other types. The Shirojuku Cherry Blossom Festival is an annual event in Gunma Prefecture, and it celebrates the beauty of this unique style of sakura.
Like all flower events, the dates can fluctuate slightly from year-to-year, but plan for around the late April timeframe. Last year's event was scheduled on the third Sunday of the month, but an official determination for this year will be made closer to the blooming season.