Setting: The fandom is set in 1990s Japan [as well as the demon world], though I haven't narrowed down how far ahead of the series's start I intend to set the story
I know that I can probably do all the hand-waving I want for this story, but I'd like to have the details and description to add to the feel.
The character in question is a demon, but the tendency seems to be to align her culture with traditional Japanese culture. So instead of inventing a random demonic plant as a contraceptive, I'd like to incorporate a technique from traditional Japanese medicine to prevent pregnancy. To make it more difficult, they reproduce asexually, so I'm specifically looking for something that would interfere with implantation or end the pregnancy very early. I assume I'm going to be looking at some sort of herb, so that's what I've been searching for.
I wasn't having much luck finding anything about contraceptives in traditional Japanese medicine. I'd remembered hearing about Queen Anne's Lace/Wild carrot, and while it looks like it would work in the way I would like it to, I am not sure if it would be found in China or Japan, or if it would have been used as a contraceptive in those cultures. Mugwort is a part of traditional Japanese medicine, and can be used as a contraceptive, but I can't find any non-Western-based examples of it being used to confirm this.
Any help with what contraceptives might be used and how they might be used would be appreciated.