A device(smartphone, tablet) that conforms to the NFC Forum's official NFC standard is required. (→Check NFC N-mark)
Because FeliCa is not NFC-A/B. FeliCa and NFC-A conform to the international standard NFCIP-1 (ISO/IEC 18092).
If your device complies with this standard, your device can read FeliCa that is not NFC-A/B.
However, the android app cannot automatically determine whether your device complies with this standard. Please make sure you have a compatible device. If your device supports "True" NFC, you will surely be able to experience great performance.
If you can't get a FeliCa-compatible device, you can still connect the NFC card reader Sony RC-S380 PaSoRi via USB.
Please purchase it on Amazon.com, etc., along with Mini-B to Type-C (or microB, Jack shape for your device) cables.
Android 5.0 (Lollipop) or later is required for TLS 1.2 required for HTTPS, so please prepare a device with Android 5.0 or later.
The models from Winter 2019 to Spring 2020 are equipped with Android 9 or 10. Android 5.0 is a very old version.
The faster the CPU, the more comfortable it runs.
The more memory capacity (not storage capacity but RAM capacity), the more comfortable.