The one who tried to sabotage the search for Akemi's time capsule is
Gaku Yanagimachi. He wanted to keep people from finding the time capsule since he thought Akemi had hidden a confession about what Gaku and his two friends had done in elementary school. They were the ones who had caused the fire in the music room 14 years ago by accident and Akemi witnessed them. On the day of graduation, Akemi told Gaku to
Be brave, which he misinterpreted as her wanting him to turn in. Years later, a few days before the class reunion, Yanagimachi went to Akemi's apartment so he could ask her to not tell anybody about it, but found that the apartment seemed to have not been occupied for a long time, although he didn't know she died. Thus, he sent invitation letters to the two others so he could use them as a cover to dig up the time capsule by himself and take out the possible incriminating evidence of his past crime.
It turns out that the time capsule was not in the equipment room, but in the breeding hut. The evidence is the fact that her name on the cipher was written vertically, and not horizontally, like the rest of the cipher, and since she used to be a member of the library committee, Conan deduced that her name represented her, and the cipher represented the computer keyboard of the library. All they had to do was input the four lines of cipher in hiragana on the keyboard to get the letters formed by each sentence on the keyboard. The letters formed were しいくごや (Shiikugoya), which meant the breeding hut (飼育小屋). After Yanagimachi confesses, Murata reveals he had copied a painting from Akemi and that his's got hung in the principal's office instead, and thought that Akemi might be angry about it and write about it inside her time capsule. Ichihashi also says she had cheated on Akemi because she looked at her copy in a Japanese examination. After they unearth the time capsule, they find a postcard from Akemi which says she wishes everyone's dreams to come true.
Yanagimachi also finds out the fire wasn't caused by him, but by the air conditioning being broken, and that Akemi's message to him was for him to stand up for himself and stop hanging out with bad people. Seiko remembers that after she cheated on Akemi and that both got scolded, Akemi offered her help to study, which helped her greatly in her grades. Murata finishes by saying that maybe she didn't enter the art competition because she wanted him to believe in himself more. The three of them then wish they could meet her again, not knowing what really happened to her.
Rumi watches Wakita leaving after he delivered the sushi. Wakita knows that Akemi was in the 19th graduating class, but muses to himself that a dead person would not be able to appear at their reunion.
