Trek to Yomi has many different trophies and achievements that you can unlock, one of which is Big Bertha.
Big Bertha is a trophy achievement that requires the player to kill 3 enemies at once using the ozutsu
This one is a real simple one to unlock and all of which can be started and completed during Chapter 4.
You will acquire the necessary Ozutsu weapon close to the end of Chapter 4, after crossing the wooden platforms and defeating the enemy target at the end.
The Ozutsu is a slow but strong long ranged weapon and is one of the requirements in order to pull off this particular trophy achievement.
We will now need to eliminate a total of 3 enemy targets all whilst using the Ozutsu weapon. However, we must eliminate all 3 targets using only the single shot.
We can find and perform this next task on the screen right after getting the Ozutsu weapon. Here there will be a bunch of enemy targets.
Make sure to align your targets up so that you can eliminate them using the single Ozutsu shot.
Note: If you fail to perform and unlock the trophy achievement then just simply reload the checkpoint and try again.