Some of the locations in Japanese Alps are relatively easy to access and I think this is a good day trip. Buses from Takayama (高山) to Shin-Hotaka Onsen are relatively frequent. A more 'traditional way' is to hop from bus to bus from Toyama and Murodo, but it is probably much more crowded... Please note that you need to be prepared - and do not count on the 'mountaneers information' at Shin-Hotaka Onsen (新穂高温泉) near the bottom ropeway station. I am sure they have very useful information but there was no one there at all - just some notices on the closed door (all in Japanese...).
Shin-Hotaka ropeway gets you over one kilometer high in 30 minutes (two stages, from 1,117 m to 2,156 m). The views from Nishi Hotaka Guchi (西穂高口 - the top ropeway station) are quite spectacular (but, I hear, you need to be lucky - or you may end up on the observation platform in the middle of the cloud...)
The trail to Nishiho Sanso (西穂山荘 - at 2,385 m) is relatively easy to find and follow but it is quite steep and sometimes difficult, please do not go unless you have at least proper hiking boots and a supply of water. The information that I've had was that it takes two hours to get to Nishiho Sanso, whish is correct - I got there in 1 hour 50 minutes; there is a nice small cafe in the mountain hut - you can get a cup of hot tea and re-supply on water. The views from there are quite spectacular - taking into account that you are standing above the clouds... The trail from Nishiho Sanso down to Kamikochi (上高地) is relatively easy (apart from several rocky places where you have to climb down) and takes about an hour. I would not want to go the other way though (up from Kamikochi)...
An important note - when you get to Azusa river you will not be exactly in Kamikochi, so please allow for some more time to walk from Tashiro bridge to Kappa bridge, where the bus terminal is. A 'general outline' of the trail is presented on the map extract below: