Previously, my speculations regarding Rumi wasn't set on one direction, since her whole deal was quite ambiguous. At the moment however, recent developments had clues that pointed more towards one direction. Rumi was at first suspected to be Asaka or Vermouth, but after picking up more clues, it's looking like Rumi is more likely to be Vermouth.
Similarly to Wakita's introduction, Rumi's introduction also seemingly has a lot of setup towards it. Just like how there were indications that the Soul Detective case was a setup for Wakita's intro, the "betrayal" series(File 954-957) has also many hints that it was setting up Rumi's intro and that Rumi is Vermouth. One of them is the fact that it was a "whisky trio" case
(Rye/Bourbon/Scotch), where Vermouth was interested in Subaru(Rye)(File 954-957), which fits with Rumi's whisky reference and that it's her favorite drink
(possibly Gosho's attempt to create a link to that case and to also foreshadow Rumi's person of interest)(File 967).
Another one is the fact that Vermouth found out that professor Agasa is Subaru's neighbor(File 955), which fits with the fact that Rumi showed interest in Agasa
(the neighbor of the man Vermouth is suspicious of)(File 966).
There's also something else, that I failed to notice before, that not only strengthens the introduction foreshadowing, that Gosho possibly used during Rumi's intro
(as mentioned in my Rumi discussion), but also ties it to the Betrayal series. Gosho established a parallell between Vermouth and Kaito Kid(File 958), and then potentially utilized it panels before Rumi's intro through DB's conversation
(hinting that Vermouth's disguise is involved in Rumi's intro)(File 966).
As for the new developments, the strongest indicator that Rumi is Vermouth is the fact that Rumi triggered Haibara's BO sense(File 978). When Subaru triggered Haibara's BO sense, the only living man that was confirmed to have triggered her at that time was Akai. Similarly to this, the only living female character to have done that before Rumi is Vermouth.
Beyond the fact that Subaru and Rumi were setup to be the main suspects of their respective arcs, they are very similar in how Gosho is developing them. For example, both of them were in an Ayumi-hostage-situation where they had to rely on their own experience to create an opening against the culprit. Subaru's being crime-related knowledge(File 666), and Rumi's being murder
(Which Vermouth has experience of)(File 989).
Gosho is even repeating the whole deal with how one person is suspecting the red-herring, while the other isn't. In Subaru's case, Haibara had a suspicion, but Conan rejected it(File 624), while in Rumi's case, Conan had a suspicion, but Haibara rejected it(File 989).
All of these parallels between Subaru and Rumi are most likely intentional, since Rumi's story might be leading to a similar development as Subaru's, where she ends up being a character, that we already knew, in disguise.
As I mentioned in my Rumi discussion, when she invited DB to her house(File 978), her goal was probably to get more information on Subaru. Since she bought cups and plates for a group, we know that she was expecting the DB to tag along with Conan to her house. Since she sensed that a crime was gonna happen, by inviting Conan and DB, it is guaranteed that Conan would go and investigate it
(like in Betrayal), which would give Rumi an opening to pry on Subaru through DB. If for some reason the crime didn't happen, then her pre-established plan of dropping them off one by one at their home becomes the opening for her to get information on Subaru
(which wouldn't have been possible in the first scenario, since the police would have taken them in for questioning and then dropped them off themselves).
The developments in the latest Rumi case(File 987-989) suggested that Rumi possesses something that is connected to the Kohji case. This seems to imply that she has a personal interest in that 17-year-old case(rather than her just wanting to confirm Conan's Kohji investigation). During the betrayal series(File 954-957) Vermouth's actions suggested that she wanted to get involved in Bourbon's mission in order to investigate Kohji's dying message. The first indication was the fact that she unnecessarily offered her blackmailer to help with a disguise
(which naturally includes getting involved in the mission in order to oversee the disguise, like in File 852), when he could just force it from her if he really needed to(File 954).
The second indication is the fact that she still involved herself in Bourbon's mission, with a rushed disguise of Asuza, despite the fact that Bourbon was enough for the job(File 955).
There's therefore a possibility that she involved herself because she was personally interested in the dying message that involves "ASACA", just like Rumi. The object in Rumi's pocket has a shape that looks similar to a Shogi piece at first sight, but after taking a closer look at its edges, the object's shape deviates from a normal shogi piece quite a bit. The object's shape looks more similar to the missing "U" shard's shape
(that was hidden by Kohji in order to deliver his dying message).
For Rumi to possess that shard, she had to have been in the US and entered Kohji's room in Juke Hotel
(Which Vermouth would have been capable of). Since it's implied that Rumi is trying to portray herself as Asaka to Conan
(As mentioned in my Rumi discussion), it's possible that she brought that shard with her in order to convince Conan that she's Asaka if the opportunity arises
(since it would at least imply that she was there in the crime scene if she showed it to him).
Why is Vermouth interested in the dying message?
What we know is that the BO at least can interpret "ASACA" from the dying message
(since they involved themselves in the Betrayal case because of that word). For that reason, it's possible that the BO are trying to find Asaka
(if we assume that she's a woman), who mysteriously disappeared from the Kohji case. Since we know that the prototype drug of Sherry's parents was involved in that case, and since we have a mysterious disappearance of a character that the BO seems to be looking for, there's a high possibility that Asaka was also drugged, when Rum attacked Amanda, and instead of dying, another effect of the Miyano's prototype took place
(ultimately leading to her escape).
From a narrative standpoint, it makes sense for Gosho to create a character that was affected by the Miyano's prototype in order to dive into the mystery of the Silver Bullet research
(the goal of the drug that Sherry's parents were making), just like how we have characters that were affected by the APTX4869
(Sherry's research). Since we recently got more details to the "accident" that killed Sherry's parents, as well as the confirmation that Sherry's(BO's) and the Miyano's research goal were different all along(File 948), it makes sense for it to be relevant in this arc.
If Asaka was drugged, and then survived like Conan and Haibara, because of an effect that doesn't kill
(which isn't necessarily shrinking), then it would explain why Vermouth is interested in the dying message. Vermouth would have reasons to suspect that Asaka disappeared because the SB prototype didn't kill her, since she knows that the APTX prototype
(that is based on SB research remains) didn't kill Shinichi and Sherry. Since Vermouth wants to hide any indication of progress to the BO research, it makes sense for her to have personal reasons in trying to figure out the dying message, since it might have something to do with Asaka, who she wants to eliminate
(before BO finds out about an effect that doesn't kill). This would also explain why she reacted towards "prosthetic" in an angry manner, while gripping an object that is connected to the dying message(File 987). Rum, who has a prosthetic, was the reason for Asaka getting drugged and disappearing, and ultimately creating this mess that she has to cover up.
So, by having Conan think that she's Asaka
(a framed witness), she would get the opportunity to use his help to solve the dying message quicker and potentially find the real Asaka.
As for Rumi's suspicious bumping in her introduction(File 966), that Conan suspected was due to her having monocular vision, it is most likely due to her glasses. Adapting to monocular vision roughly takes 1 year
(unless the loss was gradual), meaning that symptoms like bumping your head would have been more frequent
(If she lost her eye/vision within a year) and not have stopped after her intro case. It makes more sense that what tricked her perception of distance was something that she adjusted to immediately after her intro case, which is her glasses. Adjusting to new glasses takes normally just a couple of days. Glasses has also been a very prominent part in disguises in DC, and since it's common among teachers, it makes sense that she would complete her disguise with that
(like Conan in File 2).
Her interaction with Kuroda didn't imply any prior knowledge of him, but rather just her trying to verify what he knows about her. Since he treated her like a criminal
(by asking for her permission about calling the police)(File 987), she most likely suspected that he might know that she's Vermouth in disguise. In order to get information out of him, she intentionally tried to push him into a corner until he made a slip-up, which revealed that he only read about her in the news(File 988).
In other words, Rumi was simply overthinking about Kuroda's knowledge. It's possible that Gosho was foreshadowing this development during Rumi's previous appearance. Gosho drew Conan with a reflection on his right lense while thinking
"I thought a little to deep this time"(File 979). The glass reflection could have been intentional in order to create a parallell with Rumi
(who always has a reflection on her right lense when she's serious), in order to foreshadow that she's gonna think deeper than necessary in her next appearance(File 987-989). This isn't unlikely, since the end of that Golfer case(File 980) was also setting up the events in Rumi's next appearance
(with Kuroda seeing Rumi's name in the news).
I've seen arguments saying that Vermouth would have never tried to corner a Superintendent like that, but considering that we had a scene
(specifically addressing the consequences of those actions) in which Bourbon explained to Vermouth that law enforcers can do nothing without proof(File 898), I disagree with those arguments.
During Rumi's introduction, we had a scene with Teitan Elementary School's principal Uematsu Ryujiro. This principal has only appeared once in the past, and that was during Kobayashi's introduction(File 154). This principal is full of words of wisdom, but it's worth to note that Gosho is most likely using them as a foreshadowing device. In File 154, Uematsu said
"All secrets will be revealed somehow", which directly coincides with Conan's current circumstances in which Ran's suspicion was in full effect
(leading up to Desperate revival).
Similarly to this, in File 966, Uematsu said
"People who commit sins must atone... or they will spend the rest of their lives cowering in fear... or die a dog's death". This is most likely meant to coincide with Rumi's circumstance
(who was listening to him). Rumi has shown ruthlessness of a killer at least three times now. She said the sentence of a murderer(File 968), She let a murder happen(File 978) and she even used murder experience as a way to save a hostage(File 989). These instances have all been implying that she's a killer, a sinner, and with Uematsu's words, it's implying that a dog's death is awaiting her
(since she's neither atoning or cowering in fear). This all once again goes in line with Vermouth's character, who is a sinner that is expected to eventually die for her treasures
(Ran and Shinichi).
