The so-called "Yatagarasu's Key" is a device that appears to turn from a knife into a key, and vice versa, when a switch on the end of the handle is released. The "key" portion is needed to unlock a safe in the Cohdopian embassy, revealing interior and a sort of latch hole. The latch hole is actually a second "keyhole" into which the "knife" portion of the key fits to reveal a secret back compartment of the safe. Manny Coachen used this secret compartment to hold stolen items for a smuggling ring.
Murder of Byrne Faraday
- Main article: Turnabout Reminiscence
Byrne Faraday, who was one of three people who went under the guise of the Great Thief Yatagarasu, infiltrated the secretariat's office at the Cohdopian Embassy and stole the key. However, in an unexpected move, Calisto Yew, another member of the Yatagarasu, sent the key to the police. Being the first piece of evidence directly sent to the police by the Yatagarasu, it was quickly coined as the "Yatagarasu's Key", although no one other than Yew and Coachen knew of the key's dual nature.
In reality, Yew was a mole working for an international smuggling ring, and her actions were part of a plan to get rid of Faraday. She instructed a hitman, Mack Rell, to kill an embassy staff member called Deid Mann, but the thug was caught on a security camera red-handed and put on trial for the crime. Yew then offered to be his defense attorney, telling him to initially claim to be the Yatagarasu; in court, he would suddenly accuse Faraday, who was to prosecute the case, of being the Yatagarasu.
As Yew had expected, Faraday brought the key with him to the courtroom, intending to prove that Mack Rell was not the Yatagarasu by asking him about the function of the key. When Rell made his accusation towards Faraday, the trial went into recess, and the prosecutor took Rell to Defendant Lobby No. 2 to question him. Yew then entered the room and used the "knife" portion of the Yatagarasu's Key to murder Faraday.
Later, rookie prosecutor Miles Edgeworth found the knife in Rell's hand, where Yew had put it in order to make it seem as though both men killed each other. He later used it to prove that Yew had killed Faraday due to her knowledge of the key's knife portion. However, Yew stole the key, where it would not be seen again for seven years.
Murder of Manny Coachen
- Main article: Turnabout Ablaze
Seven years later, Manny Coachen used the key in self-defense against Quercus Alba by thrusting it into his left shoulder, resulting in a deep, hemorrhaging wound. However, Alba survived and fatally stabbed Coachen with a knife of his own. He then cleaned the blood off the key, replaced it in Coachen's pocket, and left the body in the victim's own office. Alba's intention was for investigators to discover the key and use it to open the safe in the office, thereby allowing them to find papers related to the smuggling ring and making it seem that Coachen was the leader of the smuggling ring. Initially, it worked as planned. However, Miles Edgeworth's investigation unmasked Alba as the leader, with the Yatagarasu's Key being the final piece of evidence used to prove his guilt.
- The Yatagarasu's Key is unique among most other pieces of multi-function evidence in that it is given two completely separate listings in the episode Turnabout Reminiscence: one for its knife function, and later another for its key function. This is because both "pieces" of evidence were not yet confirmed to be one and the same until the following episode.