Hitomi:
Use Ein and beat Story mode on normal.

Tengu:
Beat Story mode once with each character on easy.

Bouncier boobs:
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.

CG Gallery:
Get every costume for every character.

Zack glows:
Choose Zack, and either his C3 or C5 costume, then taunt during a match.