Onne is 26 years old like anny

In that world,the monster born without really a gender so they can choose! Real transgender in there are sunner who identify as mooner Or the opposite , onne identify as a any

20 years ago a long war between the moon and the sun (literal gods in that world), onne and Anny's parents were killed (they aren't sisters) at 5 so anny followed the mooners to the hole when they got Locked up in that cave and met onne, any is actually a sunner but she hide it for her safe