This character is female and has no hymen. This may be due to a genetic anomaly or to a membership in a species that is different from that of mammals.

Thus, for example, a character who shares characteristics with birds may not have a hymen, have already laid infertile eggs and have never had a sexual experience.

---

Not applicable. Seriously, batoo, stop. Your preoccupation with hymens starts bordering on creepy. I see no practical way in which this "trait" could be used, as most of the time we only find out about the lack of hymens for non-virgin characters. Instead you are trying to invent a wheel to tag those characters who congenitally have no hymen. I don't remember a single visual novel, where we would learn such a fact, and even if there is one, It would apply to a very limited number of characters.
I will reiterate - you don't have to invent a trait or tag for every weird-ass thing you come across in a VN.