Begin by preheating the oven to 325°F and then generously grease two 8" cake pans.
Cream butter, sugar, and coconut oil for 5 minutes. Add egg whites one at a time, beating for 2 minutes each. Add salt, vanilla, sakura extract, and baking powder; mix well. Sift in flours, fold briefly, then slowly add buttermilk. Fold in pink sprinkles for a uniform batter.
Spread a 1/2-inch layer of white batter evenly at the bottom of each pan.
Employ your piping bag with chocolate batter, creating a series of intertwined branches on the cake. Shake the bag as you go, avoiding straight lines, to achieve an appealing effect. Be cautious not to overdo it, as it may weigh down the cake's center.
To enhance the appearance, add extra white batter, gently smooth the top without disrupting the existing squiggles, and then pipe additional squiggly lines.
Continuously repeat the process until the batter is evenly distributed between the two pans.
After baking for 40-50 minutes, allow them to cool in the pan for 5 minutes, then invert them onto a cooling rack.