This app is provided by Osaka City. The URL of Osaka City is as follows.
https://www.city.osaka.lg.jp/index.html

This app is used in the Osaka City Administration Online System.
By using this system, residents can easily apply for many procedures such as requesting a resident's card from the browser of a PC or smartphone. In addition, with this app, you can access your My Number card, read your My Number, etc., and digitally sign your application.

"My Number Card" is a personal card that can be obtained by a person who is legally resident in Japan.
Please refer to the following site.
https://www.cao.go.jp/bangouseido/card/index.html
https://www.kojinbango-card.go.jp/

To use this app, you need a model equipped with My Number Card and NFC reader.
This is to access the IC chip of My Number Card.