We'll go over the events in order. First, there was the disappearance of Howard Link-san. Shortly after that Adam-san was attack in his room while making a video post. Conan-kun attempted to investigate this incident only to be attacked and killed himself by an unknown assailant only leaving behind a dying message. Another video post was made by Zuko shortly before he was kidnapped, and another was made by Aoko. Obito-san spoke to Aoko in her post, making plans to meet up with her and subsequently disappeared as well. Finally, four out of the five were found alive in the cafeteria, while it was eventually discovered that Link-san had been murdered, in such a way that his mental functions and memories were temporarily screwed up after his revival.
Now with that recap out of the way, let's focus first on Adam-san's disappeance. At first Conan-kun and I both thought it might have been a murder, but the bloodstains in the hallway didn't make any sense if it had been. The bloodstains indicated that he was dragged out into the hallway and up the stairs, but after that they disappear. This actually struck me as odd for more than one reason. While we know now that Adam-san was simply kidnapped along with the others, the kidnapper did not leave such evidence when he took the other victims, even though both Obito-san and Zuko-san were pretty roughed up themselves when they were found.
Next we'll move on to Aoko-san's kidnapping. I did not have an opportunity to question her myself, but Kuroba told me that the last thing she remembered doing was sitting down to tea with Allen Walker-san before falling asleep. All of the other victims, however, specifically remember being attacked by Walker-san. This also strikes me as odd. According to what information I've been able to discover on Walker-san, while he does have another personality who has, in the past, done much worse than kidnap people, the 14th does not seem like the sort of person who would sit down for tea with some random teenage girl, let alone drug that tea in order to kidnap her. Even without that, it doesn't quite fit with the pattern of the other kidnappings.
However it does seem an awful lot like he just might be the culprit doesn't it? After all, the victims themselves are often the best witnesses. In this case however, I wouldn't be too sure. With the sort of powers people in this Facility have, it wouldn't be too difficult for someone to plant false memories in the victims while they were unconcious, making it look like it was Walker-san, or rather the 14th, who was responsible for the trouble. Supporting this theory is the murder of Link-san. Link-san is Walker-san's roommate and constant companion. With him out of the way, it's more difficult to establish an alibi.
Now, who do we know who would have reason to cause trouble for Walker-san? The answer to that is rather obvious, and I'm quite sure that Walker-san and his associates in the Black Order have already figured this out themselves. For everyone else though, the clue lies in Conan-kun's dying message: Gray.
With all of the other evidence, I have been able to figure out that this was meant to be a reference to Earl Gray Tea, which points us towards the man known as the Millenium Earl. However, that's not all. For you see, he was not only responsible, but also a 'victim' himself.
Which means it was you Adam-san. Out of all the kidnappings other than Aoko-san's, yours was the one that made the least sense. You were attacked in the middle of your post, on camera, and you were the only one who left a trail. You were also the one who seemed most positive it was Walker-san who attacked you. The cafeteria might have been barricaded from the inside, but you have acomplices who can help with that. Conan-kun's murder and his dying message on their own point to you and the Millenium Earl being the same person. You didn't want him getting in the way of your fun after all.
You made two mistakes. One was the little drama you put on last Sunday. The other was leaving Aoko-san unharmed. After all, you couldn't modify her memory to make it look like she had been attacked like the others when she didn't have a scratch on her.