Crafting is a term used after 3.0.0 to obtain items that requires using other items to make it. Craftable items are identified by the distinct icon and the background they have. Casual items are usually needed, but in the later update materials are lesser units needed in usually higher quantity.
How to Craft
On the Menu, press the middle left of the menu then press the left button. If you have a craft item that has green Japanese words on the top left, that means you have the listed materials. Press that then press 作成 to create the item (you may skip the craft animation process).
Great Success system is a part of crafting that gives you a chance to craft an even more stronger item. A Great Success is possible only when the craft item lists a possible one (if a different item appears in the rainbow section. It has a fixed low probability of succeeding, so think about the probabilities when crafting.
Secret Stone of Great Successes
These purple crystals can boost your probability. The boost rate in % is shown on the bottom left of the stone's icon. 5% is most common to obtain (in Friend Slot), 10% is obtainable as a craft and in achievements, 15% in achievements, and 30%/50% in the Premium Slots. To make use of these, click on the square at the top right when crafting an item to select a stone.
Sometimes events increase the rate of either certain or all items Great Success rate. This is the time when you craft items that you patiently waited for this event.