Devil May Cry 4 - Secret Mission 02 -- Alley-Oop
When: Mission 04: Cold Blooded
Where: Dining Room
Objective: Successfully execute a mid-air buster 5 times without touching the ground.
Completing this one requires the right skills and a bit of luck. You'll need Snatch 3 to do this. Make sure that the Lock-on is set to Type 1; you can verify this by pausing the game and entering the 'Options,' then 'Game Options' menu. Your goal is to chain five mid-air Busters using the Scarecrows in the arena. The mission is a failure if all of the Scarecrows die, or Nero's health bar is depleted. The Scarecrows here do pack quite a punch, and you can die in secret missions, so retreat through the door in this area if you're close to death.
Start by using High Roller on one of the Scarecrows, then immediately use Buster while in mid-air. As soon as that Scarecrow hits the ground, hold the Lock-on button and push the Left Thumbstick (or Analog Stick) towards a standing Scarecrow. Use Snatch to pull that Scarecrow towards you, then release the Lock-on button and use Buster. Nero can't snatch Scarecrows that are lying on the ground, so you must quickly scan the area below you for standing Scarecrows that can be snatched. Luck plays a small role here, as Nero's Buster can knock down the Scarecrows on the ground below, which could leave none standing if they were close together. Additionally, the Scarecrows can also block Nero's Devil Bringer, effectively ending the chain.
You can retry this mission as many times as you'd like, as long as you don't die during it. When you've managed to chain 5 mid-air Busters, collect the Blue Orb Fragment to clear the mission.