Theory about Asaka being Rumi
1.To start off, Rumi is around 37 and the Kohji Haneda case happened 17 years ago, that gives the idea that Rumi was 20 at the time and is an ideal age of being an undercover bodyguard. You might ask why do I think that Asaka was Rumi the reason why is that she is a very skilled fighter and also very good at deductions. Those are some good traits to be hired as a bodyguard.
2.Also another theory is that Amanda purposely hired a female bodyguard to make her look that she had a friend, secretary or a person to help her because she was old.
3.Also on file 1005, at the last panel Rumi’s body was shown on underwear and you could see some scars which give the idea that she had a very dark past.
4.She has also shown interest on Conan/Shinichi which could be seen of file 1006 and she also helped Conan with his deduction by giving hints.
5.Her name “Wakasa Rumi” is very similar to “Asaka Rum”. I think that “Wakasa Rumi” is not her original name but a world play based on “Asaka Rum”. She might be doing this because either she wants to get noticed by someone, for example Kudo Shinichi or she did this world play to lure out Rum.
6.The “unknown thing” that was on Rumi’s pocket might me a shogi piece or the “U” shard from the mirror left on the crime scene. If she took the shogi piece it could relate that she took it on purpose to either serve as an evidence or because she had some kind of relationship with Kohji
This was my short theory about Asaka being Rumi also my first ever post in here!