Add the shōchū, syrup and yuzu juice to a cocktail shaker with ice, and shake until well-chilled.
Strain into a Collins glass over fresh ice.
Top with the soda.
Float Cynar on top.
*Miso syrup: Combine 2 cups white sugar and 2 cups water in a saucepan. Simmer on medium until the sugar is dissolved. Whisk in 1/2 cup white miso until incorporated, then remove the syrup from the heat and let cool. Store in the refrigerator for up to 2 weeks.