When I updated Ongeki to version 1.21i, I inexplicably ran into the problem of getting stuck at the Aime check. If you are encountering the same issue:
I know this is totally messed up, but trust me 😃
First disconnect your network (or just kill your Wi-Fi/Ethernet) and launch Ongeki. It'll throw a fit about the network check and force you into offline mode.
Next, press the TEST button (or the corresponding key on your controller) as configured in your segatools.ini file.
Reconnect to the network. Once connected, select ネットワークテスト (Network Test). Ideally, the status for Aime should now display GOOD. If you still run into issues, simply exit the test and re-enter until the Aime status is confirmed as GOOD.
Now enjoy the game!