Hanayama Puzzle: Keyhole Lvl 4

Here is a challenging maze. At first glance, the two pieces have simple concave and convex angles on their flat surfaces. However, when the two pieces intertwine, they take the shape of a 3D maze. You must twist and turn them around. If you rush without thinking, you will come to a dead end. Be careful as you may end up going around in circles.The theme is "groove."