I've been using Proton VPN so far. The free version requires a username and password like Tunnelbear does but it doesn't appear to have a monthly data usage cap. It has servers in three countries with the free version (USA, Netherlands, Japan) which is fine if all you intend to use it for is DMM games.
The lack of a monthly cap comes in handy for me since it seems like Mist is more persistent with its region lock (or I need to turn it off at a different point compared to FKG) - the game would switch to the standard maintenance screen when I turned off the VPN at the same point as I did with FKG.
EDIT: Ok, it looks like what I had to do was keep the VPN active until I got through the loading screens and the title screen then let the home screen load.