the first few headcanons are from my post on my incorrect dcmk quotes twitter account so check that out if you want
She's half japanese and half white.
Her hair is all natural, since her eyebrows are also the same color as her hair, even in the flashback from high school so unless she's been dying her eyebrows for 20 or so years...yeah she's got natural reddish-brown hair.
It's not like she was adopted or moved to Japan because her birth name, Fujimine Yukiko, is still completely in Japanese. There are two different reasons for way he name cold be this way. Either she's a bastard/unwanted child of a white man so she adopts her mother's last name or she's got a japanese father and a white mother and she just uses her father's last name like most people.
Yukiko being half white with what seems to be canonically some euro-centric features would have helped her career boost a bunch on the international level. It's fucked up but people of color, especially asians, have a very hard time entering the international acting scene. Detective Conan tells us she's picked up awards from all around the globe and she's got connections throughout Hollywood and Broadway.
Her success in the United States would be easier for the western media to stomach if she had a white parent and could speak English. Unless Detective Conan suddenly doesn't have xenophobia and racism, she would have faced hurdles.
She bonds with Ai about the discrimination they face because of how they look both in Japan and in the US.
Shinichi used to demand Yukiko to read him the original Sherlock Holmes books written by Arthur Conan Doyle in English as bedtime stories, which she did
Yukiko was a child actor.
Now I know canon says that she debuted at 18 but that really does not make any sense what so ever for her to get like every single godamn award at that age. I think that she started out as a small time child actor in Japan but then her talent catapulted her into national fame by the time she started junior high.
The movies she was in Japan became hits internationally once she became a teenager, kind of like how Parasite blew up despite the language barrier. Some of the shows she starred in were dubbed into English because they became so popular but fans outside of Japan wanted her to star in something bigger.
Once she got into high school she began her international career, starring in Hollywood blockbuster after Hollywood blockbuster. She guest starred in some American TV shows and was so popular her characters became recurring characters. Yukiko even took part in a Broadway musical for the funsies, she was on American talk shows and the general population of the USA loved her.
Yukiko built herself up from the ground, from as young as the age of four she was handling her paperwork when it came to acting. This may seem unrealistic but at least in the real life American acting industry, child actors are instructed to take care of everything themselves. Producers don't want your parents on set, they expect 6 year olds to be able to have everything in order.
Yukiko had to travel a lot for her job and in doing so she started thinking that Japan was too small for her, that she wanted to see the world, all the interesting things outside of her boring neighborhood where the same things happen day in and day out. It didn't help that her parents would travel with the money Yukiko had made, so when she had her own son she began to do what her parents did and also what she had wanted to do since a young child. Little did she realize that her son was not her, that her travels would hurt him in a different way than it hurt her.
Teitan was a really accommodating school and took her absences in stride. Yukiko was on good terms with everyone there and was pretty good friends with Kogoro and therefore friends with Eri by extension since wherever one of those two went the other would follow behind trying start up some shit. This is why Teitan is so okay with Shinichi missing school for months, because his mother was similar. This is also why the school is so good at hiding info about Shinichi coming and going, since they had to hide stuff about Yukiko from the media back in the day.
Yukiko can hold a tune but she's not phenomenal at singing either.
She's not as bad as her son, she a little above average to be honest but her acting skills made up for her pretty normal singing when she starred in a Broadway musical. The only reason the musical did so well was because of her popularity.
She helped a lot of other people in broadway with their acting skills which is why even though she's nothing remarkable when it comes to her voice, she's still well loved by the industry.
Her first love was Yusaku and she never had a crush before him. all she really cared about was her career but she loved Yusaku so much she quit. Sometimes she regrets quitting because she misses being on the stage or the big screen or even the small screen but she never lets her husband or son know about these doubts because she's terrified of what their reactions would be.
Shinichi was not planned and Yukiko knew that if she were to raise him that would mean leaving her job at the height of her career but Yukiko felt like the baby inside of her was the light of her life and for him she would destroy the world, yusaku and herself if her child desired such a thing.
Yukiko knew Sharon (who we know as Vermouth) since Yukiko started to trickle into Hollywood but she only started to feel attracted to the woman long after she'd gotten married and had Shinichi. She never voiced her feelings but Yusaku found out anyway and they talked about it. They decided that the healthiest option was for Yukiko to tell Sharon about it in order to get it off her chest when they got the news that the actress had died. When Yukiko found out that Sharon was actually Vermouth it took a real toll on her mental health, not that anyone except Yusaku knew about how hard she took it.
Yukiko and Yusaku both partook in polyamory in the very early stages of their relationship though once they had Shinichi they stopped until they decided Shinichi would be able to chose because they valued his opinion and if their son wasn't okay with the idea that one day the media might unveil that the kudo couple were part of the Hollywood sex scene then they'd decide not to go back into the whole mess. At age 14 Shinichi told them they could do whatever as long as he didn't have to hear the details.
Yukiko wanted to pull Shuichi into a relationship with her and Yusaku, citing that the couple and the FBI agent only had a 5 year age gap Shuichi said he wasn't interested in anything romantic or sexual after Akemi died so the Kudo couple respected his wishes
Yukiko would spend time asking Shuichi questions about the FBI and about himself and observing the man in general whenever she came to check up on his disguise and once she got back to the US she would give Yusaku her notes who in turn wrote the screenplay for "The Scarlet Investigator". Yukiko suggested adding a side couple that owns the house that the main character rents, based off of Yusaku and Yukiko, which Yusaku does by inverting their genders and changing their nationalities to suit a western audience.
Yukiko breaks several laws to make sure that Conan's identity is not outed.
She has Jii and Kaito to mess with security footage, she pays off witness who see him and makes them sign NDAs, and Yusaku does this as well though he does it to a much lesser extent because Shinichi's more likely to get angry at Yusaku for sticking his nose into Shinichi's case than Shinichi would be angry at Yukiko
If Ai ever needs some banned substances that Agasa can't get in order to create the antidote, Yukiko sends her what she needs in bulk
Yukiko will forever hate herself for not realizing Shinichi had gone missing for 2 weeks. If apotoxin worked properly Shinichi would have died and Yukiko wouldn't know because her and Yusaku had turned their phones off for a month straight and only came back to Japan when they turned their phones on again to see that Agasa had left them a message about Shinichi turning into Conan, Ran had texted them asking if they knew where Shinichi was and the school wanted to know why Shinichi was absent
Yukiko continues to bribe Kogoro throughout Conan's stay at the Mouri Detective Agency but it comes to her surprise that Kogoro had saved almost all of it into a college fund for Conan, implying that Kogoro does not plan to give Conan back to his original parents if they ever decide to show up again.
sorry for this word vomit lol