I don't no if it works on the ps4, but on the ps3 you can use your smartphone with the beyond two souls app.
Edit, from the guide :
2 CONTROLLERSOFFLINE CO‑OPMISSABLE
You'll have to complete the entire game while playing in Duo Mode setting to earn this trophy. Playing in Duo Mode requires a second controller or a controller + PS Vita as a second controller via remote play. There is also "Beyond Touch", a mobile application which can be used instead of the second controller but it's currently not recognized by the PlayStation 4 version of the game however that may be corrected in an upcoming update.
You don't have to find another partner to do this mode with, you can do it by yourself with 2 controllers because you usually will not play with both characters at the same time. Be careful not to switch your mode setting while playing the game because it will cause you to start a new fresh game for this trophy. You can switch to Duo mode by going to the main menu, then by choosing "Game Mode". Don't use chapter select to play in Duo mode, you have to start a new game in Duo mode and finish the game to get this trophy. Once you finish the game in Duo Mode, the trophy will unlock.