The "bittersweet, mysterious story" revolves around Chocolat Aikawa, a chocolatière who runs a shop called Chocolat Noir. She can grant wishes to the troubled people who visit her shop -- if they give her something precious in exchange.
In the Chocolat no Mahou (The Magic of Chocolate) series:
V.01 - Chocolat no Mahou
V.02 - Bittersweet
V.03 - Creamy Sugar
V.04 - Dark Spice
V.05 - Evil Essence
V.06 - Fruity Flavor
V.07 - Guilty Crunch
V.08 - Honey Blood
V.09 - Ice Shadow
V.10 - Jewel Syrup
V.11 - Knocking Egg
V.12 - Love Flake
V.13 - Melty Night
V.14 - Nutty Carnival
V.15 - Odd Cake
V.16 - Phantom Decoration
V.17 - Queen Candy
V.18 - Romantic Flambé
V.19 - Salty Leaf
V.20 - Tricky Beans
V.21 - Under Glace
V.22 - Vivid Berry
V.23 - Witch Sand
V - Premium Collection
V - Perfect Collection
V - Tears Collection
V - Memorial Collection
23 Volumes (Ongoing)