You would need two harnesses,one that plugs into the radio then another to plug into the existing Toyota wiring. Metra does offer both harnesses.
Like the other people asked,why do you want to install it? You'll probably have to modify the mounting brackets and probably the dash opening. And going by personal experience,that radio will require you to enter a security code once it's powered up...hope you know someone at a Honda dealer willing to look up the code,especially on a radio that's not currently installed in the original vehicle.