Basically zhz's question has been answered by the loungers above - as you wear the jacket (especially zipped up) longer, it will conform to your body shape and will get you )( or II shaped opening when unzipped.
But as to many million other trivial subjects, Japanese people always have 'the' answer to your question.
This is how you get that )( or II shaped opening quicker:
- grab the top of opening with your thumbs and index fingers
- scrape and pull down along the both sides (wind flap and the leather part next to zipper rail)
- when doing so, be careful not to scratch the leather surface with thumb finger nail
- do this from time to time whenever you unzip and open up the jacket front
But as to many million other trivial subjects, Japanese people always have 'the' answer to your question.
This is how you get that )( or II shaped opening quicker:
- grab the top of opening with your thumbs and index fingers
- scrape and pull down along the both sides (wind flap and the leather part next to zipper rail)
- when doing so, be careful not to scratch the leather surface with thumb finger nail
- do this from time to time whenever you unzip and open up the jacket front