The Identity of the Murderer!

Plot
Conan then continues his revelation of the murderer, disguising himself as Sonoko with his voice changer. He planned to use Ran instead, however, he misfired, causing him to use Sonoko as of the moment.

Speaking into his voice-changer bowtie, Conan explains that he figured out the identity of the killer who attempted to kill Ran in the forest, then again earlier in the bedroom, the one who carried away Chikako right in front of their faces and chopped her up in the forest.

Conan then explains that the killer wasn't really hiding in the forest, as he proved as the killer that attacked Ran in her bedroom did not leave any trace of mud on the floor. He then reveals that the killer actually came from inside the house and was barefoot, so as to avoid leaving clues.

Conan explained that the killer went into a spare unused bedroom in the villa, went onto the balcony, cut a hole in the glass window adjacent to Ran's room and attacked. Then, when Ran screamed, he instantly went back the way he came to change and met them in front of Ran's room, looking all innocent. Conan also reasoned out that the killer that cut the hole in the window knew that there was a lock, meaning that the killer knew much about the villa and that the identity of the killer was one of them.

Conan then explains the trick that the bandaged man carried Chikako right in front of their window. He reasoned that the real killer used a prop to make it seem like he carried Chikako's body. He proved that Ryouichi was the only one who could be able to do the trick, as he was the film club's former propman and he was the one who was able to gain access to the veranda as he was fixing the roof that time. Ryouichi then tried to spot an error in Conan's reasoning by explaining how he could have carried the chopped off limbs, body and head of Chikako with him when he was helping in the search. Conan then proved that during the time the puppet was used, Chikako had her choker on and the fact that Ayako found that same choker in the front entrance, proving that someone carried her body out through the front door while the others were searching for it in the forest.

He then said that the puppet was only carrying her severed head, which he then finally reasoned the final proof as to why Ryouichi was the killer: he only looked fat on the outside, as he used this to carry her severed head underneath his shirt and the costume for the bandaged man. This is why the killer tried to kill Ran: she actually saw him with his true stature when they were searching the rooms accidentally. With that fact, he cut all the phone lines and chopped down the only access bridge so that the victim wouldn't be able to escape. Conan then reasoned out that Ryouichi called Chikako outside by a letter, in which he killed her in returned. Ryouichi's motive lies within the same reason why Atsuko was killed. Atsuko was the real writer of 'Blue Country' that Chikako claimed was hers, which caused her to hang herself in the film club room. Ryouichi knew about Atsuko writing 'Blue Country', and Atsuko even called him when Chikako claimed her award to tell him that no one believed that she made the script for that movie, not Chikako.

In his revenge, Ryouichi then got out a knife which was one of the items hidden under his shirt, including the costume he used, and tried to kill himself so that he could tell Atsuko himself that he delivered justice to her. Conan snapped back at him, telling him in Sonoko's voice that he did kill Chikako for Atsuko, but killing Ran wasn't also for her. He then told him that he was no "messenger of justice" but a "murderer fostering bad blood."