The app is is currently in public beta, and DeNA is restricting streaming to a few hours a day while it works stuff out. Viewing streams is akin to other services -- you can comment or show appreciation and it'll show up on the streamer's end live, just like in Periscope. Unfortunately, there's no archive for streams just yet, so once an event's over it's over.
"I think this is the first app that allows users to broadcast everything happening on the their smartphone device through the Internet," Akagawa tells the Journal. He's not right, as Sony added Twitch and YouTube streaming to its recent Xperia devices last month, but Mirrativ works across a wide range of Android devices. DeNA is also working on a similar app for iOS, although given the closed feature set Apple provides developers with it's tough to imagine the experiences being identical cross-platform.
If you're wondering where you've heard the name DeNA before, wonder no longer. It's a big deal in Japan, where it's behind some huge mobile titles, and also runs an online gaming platform called Mobage, which is a rough equivalent of Xbox Live or PlayStation Plus. It's such a big deal that Nintendo has partnered with it to create mobile games and build its next-generation online services, taking a 10-percent stake in the company at the same time.
Mirrativ is available in the Google Play store now, and you can keep tabs on when the streaming starts each day over on the company's Twitter.