Neat little game. I like the art and animation. Took me some time to figure out how it works. If anyone else is struggling and checking these comments to figure it out:
Fill the mixing cup with some combination of crystals from Cirno and Flandre. Once it's filled, give it to the backup mixers and they'll mix it. Then drag it to the drinking cup to create the drink. Take the result and give it to the matching "order" in the first page. At any time you can stick a cup into Mokou's microwave to reset it.