First of all thank you Duffer19 and gocchin. As gocchin said the device is good to monitor my swing speed and my swing path which may be one of the reason for being inconsistent in my swing (outside in swing) especially when i want to be aggressive to get some distance. My coach has also advise that device as such, although won't be as accurate as what you can see with your eyes in range, which i agree with Duffer19, it'll be good to have a record of your good and bad swing, especially the tempo of the swing.
So thank you so much again people and these are very useful comments. However it is also until now that i wish i know how to read japanese. :)
p/s I read through Gocchin eng manual and i'm very thankful. it will proof to be very handy in future.