This festival is a gathering at the Celesta Church Grounds to view the cherry blossoms. This is a simple "date" festival and there are no vendor selling items. Although, you can find Simon and pay him 100 G for a photograph. The festival officially starts at 6:00 pm but you can visit earlier and talk to the people.
If you want a date to this festival, you can ask a marriage candidate who has 3 or more hearts on the 13th. The person will ask if you would meet them at 7:00 pm to view the blossoming trees. You can only invite one person, and you can't change your mind once you've selected your date.
At 7:00 pm be at the Grounds square and head towards the blanket to the left of the church staircase. Your date event will trigger and everyone will watch the flowers. The festival will end at 11:00 pm.