Hi hello_ebear!
HHBB was such an incredibly experimental game, I'm not sure we could truly answer that question accurately.
I'd estimate at least an i5 processor, as well as a gpu somewhere around at least a 960/970/980 and above.
The good news is, you will definitely be able to experience the story in the near future, in a little bit of a different aspect that will be much more optimized! Stay tuned.