In line with @Laguz’s reply, there is a difference between being asexual and being aromantic. One person can be both, none or a single one (or just degrees of it).
Some threads to take in consideration:
https://forum.choiceofgames.com/t/asexual-characters/16558
The first one has many links and info on asexuality, the second one has an interesting discussion around being “sexual aromantic”. Feel free to read them and get to know to variations and what they mean a little better.
Glad to help and good luck with the story. It doesn’t seem my kind of game-book but I will make sure to check on it from time to time. Congrats on the initiative and on the original idea 
By the way, don’t take my post as a request/demand for having those orientations in your story, it is your story after all 