How to fix transparent models in Cycles

When using Cycles, if the model has two or more meshes in the same place, it might become transparent.

This model has blush mesh on top of face, and skirt has backside mesh.

To fix this, you need to separate meshes by materials, hide blush (016照れ) and move back side (00L裙-裙面+) a little bit to prevent clipping.

credit: 星尘 by 椛暗