Or just do it all on the browser and have it DL to your PS4 when you turn it on. =)
Edit:
Go to ゲーム ---> 体験版
Since I dont log in through the web often I just do everything through my system. So its more for those folks. Otherwise wouldnt have bothered saying anything as the link is already in the OP for the browser crowd.
Reason people cant seem to find it (well those who are accessing the JP store anyways) is that the demo isnt in the standard demo section yet for whatever reason. It appears in the New Arrivals - Demo section sitting there with the Valk spinoff and DGR 3.
Wonder if the update to the actual demo page is slower or something. As weird that it was not on there when I checked 10 mins ago and had to go to the New Arrival section instead. Doesnt make sense though since the whole system is automated as long as everything is locked and loaded with the settings and files it should put everything into the proper places at time of update. :/