Angry

Kill 100 enemies during your Time Rewind Berserk buff.
Any time you're attacking enemies - either melee attacks or shooting attacks - you can hold down L1 Button until you see another Ayumi appear onscreen; let go of L1 Button and you will have another Ayumi onscreen attacking the target you've been attacking; as the "time rewind" function winds down, your screen will start to go a deep red colour, and it is during these moments that your "Berserk" buff is active - if the enemy you're fighting dies during this buff, the kill will count towards the trophy.

There really isn't a need to farm this as it will come with time, and it will be very helpful to you on your hard playthrough to make extensive use of this ability in combination with your machine gun to help thin out groups of monsters, especially heavies - multiple Ayumis firing machine guns into mobs will make quick work of even the most difficult situations.