Male protagonist 27
The heroine is gloomy, a bit stubborn, a sorcerer who can be regarded as a physical practitioner, and is the disciple of Mukuro.
It is set as an original fanfic. The heroine was accidentally rescued by 27 and wanted to become stronger. After meeting her, she entered Valia according to Skeleton's instructions.
Heroine's ability: The ultra-low sense of presence makes most people unable to see her aura even if they stand in front of them.
Set 8 years after the original work
Anyway, I don't know how to introduce it, so just read it as a fan fiction.
Purpose: Upright patriotism