There are two parts in the game, heaven where you start and then hell where the game ended. You can either skip almost all battles and just stack up your urne and get to the next stage and do the same there to finish the game which should take about 30 minutes or 1 hour to finish (if you are unstoppable!) or you could spend time with some of the side stuff like helping a lady off a cloud, finding "diekiru" or stealing stuff and selling urne to get better weapons. There are also some additional characters that can help you fight for some of your Urne. Then the game would probably take up to 2 or 3 hours to finish.
I beat the game a few time both ways but apparently most people complained that the game was difficult to understand and the map was confusing (it wraps around both ways like in Yume Nikki games) .
Please comment if you get stuck, I might make a walkthrough.