Dead or Alive Ultimate
Use Leon and beat Story mode on normal.
Use Ein and beat Story mode on normal.
Beat Story mode once with each character on easy.
Go to 'Settings,' then 'Game Settings,' then 'Others.' The 'Your Age' section really toggles boob bounciness, and the higher you set it the bouncier boobs will become.
Get every costume for every character.
Choose Zack, and either his C3 or C5 costume, then taunt during a match.
Special thanks to Revolution readers Noah Tsutsui, Aaron, Sasian, and AndrewM!