Hi Yorune, there are cosplay events taking place every weekend in the Nagoya area, you can find information on them on Cure or Archive. Here is a link for an organization that organizes cosplay events around Nagoya and the Osaka area: http://www.cosjam-revolution.net/
The web page is only in Japanese but if you have a friend that can help you navigate then you can get out to the events.
Youyou is an organization that puts together Doujinshi events around the country, here is their calendar for the Nagoya area:
They have events twice a month and you can cosplay at their events. Again these sites are only in Japanese so go over it with someone who can read Japanese if you cannot yourself.