I'm not 100% sure how to open the seat on your Honda but if it's anything like my Yamaha majesty then put the key fully into the ignition. Do not push down on the ignition with the key. Slowly turn the key anti-clockwise, you should feel the cable for the saddle lock being pulled and the seat should pop open.
This procedure maybe different for your bike but if you have an owners manual then the instructions are in it.
Steo, November 2009