super interesting item !
i did some research and apparently you can change the m/s to mph via pushing the mode button and then arrow:
"Only downside is the instruction is in Japanese but it is pretty easy to figure out. You click on "Mode" and "Up" arrow to change to mph & yards from m/s and meters. "
from an amazon review comment
i also saw on the previous version of this launch monitor to change tp mph you needed you long press the menu button several time (cycling between different mode).
Other people are talking about another brand as well, looks very similar : yupiteru. about the same price ranges but they have more models (owing to one post, this brand is more popupalr in japan for launch monitor than the prgr ones). the easiest to find is the gst-5. In the gst-4 manual it was written you could change m/s to mph in the settings menu. for gst-5, in its manual, this particular section on settings does not exist.