Preheat the oven to 325°F. Grease a 9-inch springform pan.

In a medium bowl, mix the graham cracker crumbs and melted butter until the crumbs are evenly coated. Press the mixture firmly into the bottom of the prepared springform pan. Bake for 10 minutes, then set aside to cool completely.

In a large bowl, beat the cream cheese with an electric mixer on medium speed until smooth and fluffy, about 2-3 minutes. Gradually add the sugar, beating until fully incorporated. Mix in the sudachi juice and heavy cream until combined. Add the eggs one at a time, beating well after each addition and scraping down the sides of the bowl as needed.

Pour the filling over the cooled crust. Bake for 55-70 minutes, or until the center is almost set (it should still have a slight jiggle).

While the cheesecake bakes, make the topping by whisking together the sour cream and sugar in a small bowl. Once the cheesecake is done, remove it from the oven and immediately spread the sour cream topping evenly over the top. Return it to the oven for an additional 10 minutes.

Turn off the oven, prop the door open slightly, and let the cheesecake cool in the oven for 1 hour. Then, remove it and let it cool completely at room temperature. Refrigerate for at least 4 hours, or overnight, before serving.