I went to the police on Thursday evening, told them about my situation and that I was concerned that I was about to be a victim of blackmail. She had threatened that she would go to the police and accuse me of rape or revenge porn, but deleted the LINE messages before I could screenshot them.
I deleted all of "those" photos / videos that we had taken together as a precaution after that threat. She seemed to know some details about conversations that I was having with other people, so if she had compromised any of my accounts, I didn't want her to post those photos / videos herself and claim that it was my doing.
The police refused to take a report without hearing her side first, and insisted that they needed proof that we had separated and that I had told her that we were over (we were never in a proper relationship) before they could consider any of her behaviour to be stalking. They also said that her written threats were not substantial enough to take any action, since they didn't explicitly contain threats of bodily harm or anything of that sort. I do not think they took it very seriously, since the threats were all written in Korean, which they couldn't (or wouldn't) translate, but it is true that her threats were more foreboding than explicit.
Finally, they said that they needed proof of her pregnancy first before they could really do anything, since if she were pregnant, and I were the father, then I would have to speak with her directly or via lawyers. I was really hesitant to escalate this further, because I didn't know how explosively she might react, but I agreed in the hopes that there would be no proof and this could be put to rest. They went to her apartment and questioned her, apparently got no solid proof of her pregnancy, but she did seem to have told them that I was about to (or already did) post revenge porn of her. So they visited my apartment at 1:30AM, and asked to search my phone and laptops (can they do this without a warrant?!). I stupidly let them do that, and they seemed satisfied that I had deleted all the videos and photos that she was concerned about.
Yesterday the police called me and said that I should go to the hospital with her next weekend to confirm the pregnancy. I declined, since that just gave her more time to make up excuses or come up with other schemes (she had previously asked me to bring a hanko or an identity stamp of some sort, without knowing that I wouldn't have such a thing as a foreigner). The police then said that she had promised to get a new ultrasound next weekend and that they could review and then present the evidence to me separately. So I'll wait for that to happen instead of trying to meet her and falling victim to another scheme.
They also mentioned that she had visited the police station again in the middle of the night, but would not tell me any details about that visit. I'm concerned that she may have tried to accuse me of other crimes.
Anyway – does anyone know any good bilingual Japanese <> English lawyers or law firms in Tokyo that could help with this sort of situation? This seems like a family law issue, but I still don't believe she is actually pregnant (why would she send someone else's ultrasound?), and I'm growing more concerned about the blackmail aspect of this situation, so some sort of super lawyer / lawfirm that could handle both would be ideal.
TLDR – Girl I used to sleep with is faking a pregnancy and trying to exact revenge on me via blackmail because I broke things off with her. I went to the police, and because they need to be impartial, they are also listening to her false accusations. I need a bilingual lawyer that can help in case things escalate further.
Thank you all for your suggestions and advice.