Before I get into how you get the Berserk game, you do have to make sure that you are able to play japanese games on your PS2. If you have, you can skip this mini introduction. So, to make sure that you can play japanese games on your PS2, you either need to have a Japanese PS2 from Japan or a modded PS2 that let's you play Japanese games. Your best bet might be going for a Japanese PS2 from ebay. For the PS2s themselves, you don't have to worry about any voltage problems, all PS2s before the 90k have an extra "power brick" that converts to whatever you need. If you get your hands on a 90k PS2 however, there is no power brick whatsoever, because the poer brick itself for the 90k, is built into the 90k PS2. Meaning you only need the cable to connect to the PS2 and to the power socket without any issues. Thats it for the preperation for PS2s. If you need any more info about the PS2s region lock thing, there should be tons of info out there. Let's now go onto the Main game.

So, you have a console that plays Japanese PS2 games, very good. Now, your best bet would be to look up on ebay or amazon to get a hold a Berserk copy. Here is a link to an ebay page where you should easily find tons of Berserk copies. https://www.ebay.ch/sch/i.html?_from=R40&_trksid=p2380057.m570.l1313&_nkw=Berserk+ps2&_sacat=0

I hope that helped :)