Japanese knives for someone who can't sharpen freehand?
You can sharpen the Japanese knife to 17 degrees.  It won't be ruined or anything.  I'm sure I just horrified some people, but I accidentally did this for years, sharpening my Victorinox knives at 22 degrees (because they're European, so obviously they're 22 degrees, right?) when they're factory sharpened to 17 degrees, so I've got real-world experience here even if I shouldn't admit it. :)

Otherwise, check out a sharpener built for Japanese knives instead.  I've had fantastic results with this model from Chef's Choice:
https://www.amazon.com/Choice-Trizor-EdgeSelect-Electric-Sharpener/dp/B0018RSEMU/