Japanese Puzzle Boxes are handmade and each box is a Masterpiece! Work-of-Art!
This box has the "Yaeasa B" pattern and 21 steps (moves) you will need to execute to achieve the right combination that opens this amazing puzzle box.
In order to open a Japanese Puzzle Box, you need to find the first piece (part of the box) you can move (by "move" we mean actually "slide"). This action causes other piece of the puzzle to "unlock" and allows you to move it too now. This is kind of a "chain reaction" where each piece you move partially unlocks other piece allowing it to be moved as well, and so on and so forth, so basically each move you execute allows you to execute your next move.
When the right movement combination is achieved, the box will open (meaning you are able to slide the top panel and open the box).
2 things you need to know
1. "Sun" is the measurement of the box - the bigger this value is, the larger the box is.
2. The more steps your puzzle box has means the mechanism is more complex and therefore the box is more challenging and difficult to solve!
Note: At the bottom of the page for the link above, you will see an animated solution for a 5 Step Japanese Puzzle box. This is a great example to better understand how the mechanism for these kind of puzzles work.