Its possible to get away with dropping the last leg, often referred to as throw-away ticketing. However, in your case, you are dropping the first leg. This will invalidate your entire itinerary the moment you miss the first flight. Don't do it
Why not buy a cheap one way ticket to HKG instead, Peach flies from KIX i'm pretty sure. Boom, now you have a quickie vacation in Hong Kong and your costs are the same as buying one way from KIX.