Well, it wasn't from SA, which was what I was expecting it to be when her scars were first revealed. This removes the possibility that SA led to her being sexually averse and she is just asexual while also having childhood scars+trauma on the side (By no means am I insinuating that all SA causes asexuality or SA is the only reason for asexuality or other bad takes, but people can grow from experiences)
In any case, still very interested in this. Also interested to see if they are aromantic to some degree. Also also interested to see if Matoi will ever try sex, since she is still learning about it as opposed to Yuriko who seems much more secure in these aspects.