can i put my web in webhosting at USA if i want to make business in japan（my target users are japanese,and language in page is japanese)? will google discriminate my web or to what degree?
Through Webmaster Tools you can geo target your site to any country. There are many sites hosted outside the US that do well in the search results here. It may help to be local but that can be overcome. You can also geo target subdomains or folders so you can reach several countries. Hope this helps
SERP is not only based of IP of country. its based on niche links too. there are many country those are not having Datacenters. but they ranked well. Thanks for comment on my Avatar
Actually the location of web hosting account is not a main reason for SERP. but ip may be a reason. (Not too much), Try to keep web sites in quality.
where it is hosted doesn't matter.just having it in japanese tells what target you want. using jp TLD will give it more weight. if you only want people from japan,go into webmastertools and you can tell them to target just japan,but if you welcome people that speak japanese from any country,i wouldn't do that.
I am not sure how Google would rank websites hosted on specific IPs so I can't give you a clear cut answer. But if you want to target your Japanese Learning website to Japan, why don't you GEO TARGET your traffic? Just login to your Google Webmaster Account, and you will find the GEO TARGET menu to choose from. It won't hurt if you add more countries too! I had a friend in UK that would do anything to learn Japanese