depends, you want to see everything in the game? you probably need 2 gameplays, considering there's way more scenes than days  

¯\_(ツ)_/¯

But jokes asides, considering some content is exclusive to some stats[like charm and innocence] and choices the player might have if you want to do/see everything you will need 2 gameplays. I always recommend going for the true ending and enjoying before going full collectionist  and up every stat and find everything in this game