Operation Cat Killer (操作キャットキラー, Sōsa kyattokirā) is the unofficial codename given to the unsanctioned mission to assassinate Gengo Aoi, given to Radox Phantomheim by the Chevalier in 2065. The execution of this mission resulted in the 13th Nova Clash and has since ended in failure.
Following the 12th Nova Clash, the Chevalier council grew concerned with how many secrets Gengo Aoi had kept from them following the introduction of the Legendary Pandora. They feared that Gengo would attempt a coup d'etat and take control of all their authority concerning the Nova threat. In reality, their fears proved correct as Aoi began to gather personnel and soldiers to his headquarters in Japan. Commander-and-chief Alfred Hughes, long time associate of Gengo's, blocked the Chevalier from taking immediate action against the doctor.
- Radox Phantomheim
- Sawatari Isuzu (Captured)
- Petty Layner (Deceased)
- Isabella Lucas
- Jessica Edwin (Presumed Deceased)
- Main article: Busters Arc
Fearing that Gengo Aoi will completely usurp their position as the leading defenders of mankind, certain members of the Chevalier secretly plan "Operation Cat Killer", and enlist ex-Commander Radox Phantomheim to carry out the assassination. Radox plans to utilize the "Failure List," mentally unstable former Pandora, as assassins to kill the doctor. The Chevalier equip members of the "Failure List," now dubbed "Busters", with experimental Plasma Stigmata to give them an edge over Gengo Aoi's own private Pandora army.
The Busters infiltrate Gengo's headquarters after an amphibious insertion from a submarine. The group is confronted by Chevalier squads but are able to neutralize them. They soon run into Genetics Pandora Satellizer L. Bridget, Elizabeth Mably, and Arnett McMillan as well as their respective Limiters. Jessica and Isabella stay to deal with the Pandora while Isuzu and Petty continue on with their mission. Gengo is quickly alerted to their presence, and he deduces that Radox Phantomheim sent them to silence him. After observing their use of Plasma Stigmata, Gengo orders the evacuation of all Pandora and staff. When Su-Na suggests he evacuate as well, Gengo refuses as he believes that this is Radox's message to him that he can deal with Gengo whenever he wants. The doctor refuses to be cowed by such tactics. He deploys the Valkyries to deal with the assassins. Unfortunately, when the Busters utilize their new Freezing abilities on the Legendary Pandora it causes the majority of them to go berserk. As a result, Gengo cancels the evacuation and instead orders the Legendary Pandora to be neutralized.
Due to the severity of the situation, Gengo decides to make his way to West Genetics to awaken Maria Lancelot to deal with the Legendary Pandora and the Busters. He is escorted by Su-Na and two other Chevalier Pandora. Before they can reach the transport however, Sawatari, who has actually killed one of the Busters, ambushes them. She attempts to kill Gengo, but Su-Na manages to protect him. The Buster quickly eliminates his guards, leaving Su-Na as the only thing standing between Gengo and his assassin. In order to protect Gengo, Su-Na agrees to allow herself to be brutalized by Sawatari, who only agreed to take part in the operation to meet Su-Na again. As Sawatari begins to savagely beat his bodyguard, Gengo explodes and claims that Sawatari is not worthy of being a Pandora, and that he will never forgive her. In response, Sawatari quickly tackles Gengo to the ground, breaking her promise. Gengo is unable to fight off the Buster's advances. Su-Na quickly moves to attack Sawatari from behind, but is cut down mercilessly. Wounded but alive, Su-Na tries once more to convince the assassin to leave Gengo alone, only to be laughed at. Before she can make a move, Sawatari is interrupted by the arrival of Scarlett Ohara, whose own bodyguard Amelia Evans moves to engage Sawatari. Amelia proves a match for the assassin, and slowly begins to push Sawatari back. She stands down however, and to the horror of Sawatari, steps aside to allow Su-Na, upgraded with a Legendary Stigma System, to resume the battle.
At the plaza, Jessica and Isabella confront Cassandra, but their actions are fruitless and Cassandra releases an Anti-Freezing that begins to Novalize Jessica and Cassandra dissolves one of Isabella's arms with a particle beam before summoning 5 Pandora-Type Nova. With the Legendary Stigmata System, Su-Na defeats Sawatari by severing her arms after learning that she is now able to deploy the Illusion Turn. The 13th Nova Clash has begun as a direct result from the Chevalier's assassination attempt. With Petty dead, Jessica Novalizing from an Anti-Freezing effect from Cassandra, Isabella fleeing the scene, and Sawatari's defeat, the Busters' assassination attempt on Gengo has been deemed a failure as the doctor, alive and well, is en route to West Genetics.
- The term "Cat Killer" is unofficial, and is taken from a conversation between Radox Phantomheim and a Chevalier agent where the former refers to Gengo Aoi as the Chevalier's "pet cat."