Add the gin, cherry blossom syrup, lemon juice, and egg white (or aquafaba) to a cocktail shaker without ice.
Dry shake hard for 15 seconds to build the foam.
Add ice and shake again for 15 seconds until fully chilled.
Double-strain through a fine-mesh strainer into a chilled coupe. Drop 2 drops of orange bitters onto the foam surface (optional).
Garnish with a lemon slice on the rim or a fresh cherry blossom petal (or pansy flower) on the foam.