I'm not sure what you're asking. Are you asking to clarify the criteria for getting the last scene? Or are you asking for advice on how to beat the final boss?may i ask how you do that last one
In any case, the last scene is tied to which ending you get, and you're locked into one of the 2 endings based on who gets the cure. The ending with the H-scene requires giving the cure to the purple-haired girl.