Preheat the oven to 350°F (175°C). Crush the chocolate cookies into fine crumbs and mix with melted unsalted butter. Press into the springform pan and bake for 10 minutes.

Beat cream cheese and granulated sugar until smooth. Add eggs one at a time. Mix in orange zest, orange juice, and vanilla until blended.

Melt semi-sweet chocolate chips and fold into the cream cheese mixture.

Dissolve agar-agar in water over medium heat and mix into the filling.

Pour the filling into the crust and bake at 325°F (160°C) for 55-65 minutes.

Cool in the oven with door ajar for 1 hour. Then chill in the refrigerator for at least 4 hours.