In a pitcher, combine frozen berries, orange slices, lemon slices, and Akashi-Tai Shiraume Ginjo Umeshu. Let refrigerate for at least 2–3 hours (or overnight).
Fill wine glasses with ice. Fill each glass halfway with Umeshu mixture, add some of the fruit. Top off with chilled sparkling sake, stir. Garnish with mint springs and fresh strawberries.