Make objects with specific script follows an object with the same script

I want to work on my brick-breaker prototype that's similar to Block Breaker 3 Unlimited, but I don't know how to make other balls follow the ball that touches the arrows. I've tried to use transform arrays, but it keeps being screwed up.

Here's the gameplay of BB3U:

How can I achieve this properly?

 

I'm not going to watch the whole video because you didn't mention a specific time that it happens, so I'm not entirely sure what you mean, but I'm going to assume you mean at the end of the level when a sort of escape path opens up and all the balls leave the game area.

You can just use a set of triggers by the escape path arrows. Once one ball touches the trigger, tell all balls to leave the play area via a the specific path designated by the trigger itself. You can use a simple state machine inside the BallController script:

Code (csharp):

1.  
2. enum BallState { Playing, Leaving };
3.  

or alternatively, disable the BallPlayingController component and enable a BallLeavingController to handle the logic instead.