First of all, I don't know the knife, but have a few suggestions.
The original angles are rarely relevant. Often they're unpredictable, and if not rather inspired by marketing considerations. They don't take into account the use you will make of the knife, or how experienced you are at sharpening. They may be much too conservative - to avoid complaints - or much too acute - to impress.
I would suggest to thin behind te edge as much as you can. That means, get the lowest angle you have or can hold and thin til you almost reach the very edge. Verify with the Magic Marker Trick. Then, apply a micobevel at a few degrees more.
With Japanese knives you have to deal with at least some asymmetry, for example right side convex, and left one flat. In that common case I would thin only the right side, and almost just deburr the other one. Almost, because even then you've to abrade some fatigued steel in order to get a fresh edge.
Now you've got a very edge formed by a microbevel you may change easily according to your needs. To give you a very general idea: most knives will end with an inclusive angle between 18 and 25 degree.
P.S. In the long run not the best solution IMHO, but serious EP users have reported to sharpen them symmetrically at 10 degree per side.