Help please I’m trying to find a tragic yuri I’m not sure if it has a different name b...

Help please I’m trying to find a tragic yuri I’m not sure if it has a different name but it’s call giving you my all before her lover have to get marry off to a man she has to bring back the demon sword but it doesn’t happen she end becoming the demon prisoner living off the illusion that she did come back to her love the princess believes that her lover lied