Sakura season is Japan's most beloved annual event and one of the most beautiful natural spectacles on earth. For roughly two weeks, cherry trees across the country explode into clouds of pale pink and white blossom. Hanami — flower viewing picnics under the trees — is a national ritual. Parks fill with families, friends, and colleagues sitting on blue tarps under the blossoms, eating bento boxes and drinking sake. The most famous spots are Shinjuku Gyoen and Ueno Park in Tokyo, Maruyama Park in Kyoto, and the philosopher's path in Kyoto. The blossom front moves north from Kyushu to Hokkaido over six weeks — you can follow it.
The bloom window is unpredictable — Japan Meteorological Corporation publishes forecasts from January. Book accommodation 3–4 months ahead. Weekday mornings in famous parks before 8am are quiet and magical.