Add all ingredients besides club soda to a mixing tin with ice. Shake and double strain into a Collins glass over fresh ice and top with club soda. garnish with a lemon wheel.
For Yuzu Kosho Syrup:
Add ½ cup granulated sugar and ½ cup water to a small saucepan over medium heat. Stir until sugar is dissolved, then add 1 oz. Yuzu Kosho paste (you can get this from Amazon, specialty grocery stores, or Asian groceries) to the saucepan and stir more. Let cool, then pour into a glass jar and seal tightly with a lid.