MC's daily life, one of the major elements missing from the EXCEEDS Gun Blaze Vengeance anime.
The story never slow down.
In 12 episodes, it was almost entirely plot progression.
there was no time to get attached to the characters.
This is glaringly obvious when comparing it to Nanoha A's...
Actually, there is a huge difference between a concubine and a mistress.
A concubine has a socially recognized semi-marital status as a secondary partner, while a mistress is an extramarital partner in a clandestine relationship.
To put it simply:
concubine = not cheating
mistress = cheating...