This is on their news tab when you scroll down to below the game:

Thank you for playing Kamihime Project

We have received some inquiries regarding issues encountered with the releasing of Souls and viewing their Harem episodes.

We are currently investigating the situation.
Another notice will be posted when the issue has been resolved.

[Update]
We have fixed some system errors. Souls should be releasable and their Harem scenes should now play properly.

However, some system issues still remain.
These who already unlocked souls while the error was in progress may still encounter issues when attempting to use their Souls.
We are currently investigating the cause of this error and will remedy the situation as soon as possible.


We hope this helps and that you will continue to enjoy Kamihime Project.

Sincerely,
The Kamihime Development Team


I can personally say I've unlocked 2 souls earlier today, making use of the Sunday quests to level them up quickly, using the soul points from the event. Both souls are fine, and working as intended - So it's perfectly safe to start unlocking souls again, its only those who have already unlocked souls that will have issues.