WMG / In the Land of Leadale

Keina/Cayna was the beneficiary of Mind Uploading.

Cayna was online with the game long enough to get two summoning bells, which could really only be reasonably done in four years.

Due to her being bedridden, the techs that set up her would have plenty of time to adapt the system for her, moreso than anyone else.

While she was under, Mind Uploading technology was invented, but there’s not really an ethical way to test such a thing.

When the disruption that caused her death IRL happened, someone, out of compassion (and probably a desire to see if it would work), was able to get permission to use it on her. She was written into her avatar body and sent to live in a local server with the Leadale program on it. But, she only exists as an infomorph; her real body is dead.

The only thing this doesn’t explain is why the other players are there and can’t leave.

Keina/Cayna wasn't killed by the blackout...

Hospitals have very robust and sheilded electrical systems with Uninterrupted Power Supplies that are designed to keep ICU and other patients supported through blackouts. This is at least the case in the U.S. and I assume Japan is no different being such an advanced country. This would have kept Keina's life support running during the brief power outage and protected her from any power surges... except...

Keina was also hooked up to a series of components and control devices related to her Leadale game which were independant of the computer systems. These would not have been sheilded or surge protected as well as the hospital's systems. When the power came back on, there was a power surge through her Leadale PC and components attached to her (remember Keina fell asleep after playing the game and was still technically attached to it). This power surge delivered a shock to her body. While this probably would have not been life endangering to any healthy person, the shock was fatal to Keina who was bedridden and weak from her condition. It was indeed the Leadale MMORPG game that killed Keina, just as the urban legends were saying, although how much of the truth was ever really confirmed by the game operators, the hospital, and Keina's family after her death are unknown.