A sharp Japanese kitchen knife should be paired with an adequately high quality cutting board. One such brand recognized and used all over Japan is Hasegawa. Delivering high quality cutting boards that are soft on the edge of your kitchen knives, with an assortment of series and sizes. 

FSR Series

These cutting boards are made out of high quality polyethylene (plastic). As such, it makes them quite stain resistant and resilient to the occasional deep cut. Given the core is made of wood, it gives the whole board a lot more rigidity and less flex. Oddly enough even with a wood core, these Hasegawa cutting boards are still 30-50% lighter than cutting boards made out entirely of plastic.

Given this is a softer board, it is ideal for your delicate cutting of fish with a yanagiba. As the board is somewhat 'sticky', it also means your pieces won't move.

The added rigidity of the board also means it won't warp or bend if you put it in the dishwasher at high temperatures.

As for hygiene, you don't need to be worried about the wood core. It is covered and sealed under thick plastic layers and unless the board becomes grossly damaged, the core will never be revealed.

This is a massive Board at 30mm ( 1.2")  thick and 1,200 x 450mm ( 47.2" x 17.7" )