Apps for Communicating with Japanese
While there are many different apps for communicating online, LINE is now so popular in Japan that we can't think of using anything else.
Oh My Japan's recommendation: use LINE
LINE is the number one chat app in Japan. As of 2016, if you want to talk to Japanese people, LINE is usually the most convenient option, since most Japanese people already have a LINE account and they already use LINE to talk to their friends.
LINE is a free app and can be used on iOS, Android, Windows, and Mac.
The alternative: use Skype
Skype is popular around the world, but not widely used in Japan. Still, if you can't or don't want to use LINE, Skype is a good second choice.