HelloTalk is a sort of social network built entirely around the idea of doing language exchanges. Users join HelloTalk equipped with the knowledge they have of their native language, and the desire to learn a new one. With this, users help teach their native language with the hopes that other users will return the favor. While the HelloTalk app provides some tools to aid communication and assist learning, as well as different means to communicate with others and find language partners, how useful this app may be to you is completely dependent on the types of connections you're able to forge and the other user's ability to teach. The app has a variety of users from different countries and supports a number of different languages, including of course Japanese.
HelloTalk is offering something rather unique in the language learning space. It features a vibrant community of (mostly) like-minded language learners, with whom you can both learn from and help improve. I'm very thankful for the friends I've made on the app, all the positive interactions I've had, and what people have taught me, but it really is a case of "your mileage may vary." I found HelloTalk to be a really rewarding social network to be a part of, and always looked forward to sharing my experiences with others and improving together, but that's not to say HelloTalk is not without its warts. I can say first hand there's a great experience to be had on HelloTalk, but your own enthusiasm can only bring you halfway.