Line a 9x13" baking tray with silicone or parchment paper.
Arrange graham crackers in a single layer on the baking tray. You may need to break the pieces into smaller rectangles to make them fit.
Melt the chocolate and coconut oil (if using). You can use a double boiler or you can use the microwave. If using the microwave, place chocolate in a shallow dish and microwave for two 30s increments, stirring after each time. Continue microwaving 10s at a time until chocolate is smooth. Microwave times vary depending on device so please watch carefully.
Pour melted chocolate over graham crackers, smoothing out into a thin layer.
Sprinkle mini mochi, konpeito, and sugar onto melted chocolate.
Let chocolate harden at least 2 hours, but preferably overnight, before breaking into shareable pieces.