1st interview is about technical background and includes a coding test. The test isn't too difficult as non-optimal solutions are accepted and it is more for them to understand your thinking process. The bad point is that the assignment content has nothing to do with the work that you'd be doing.
The 2nd interview is at their office, with a CxO. It is more of a standard HR-like interview where you'd discuss your experiences, strong/weak points, reasons for applying etc. It also includes a tour of their facility to get a look at the product.
All interviews are fully in Japanese.