The time spent on NiOh 2 depends on your skills. On this page of the guide, you will learn how long it may take you to complete the game.
If you are an experienced player who has played soulslike games in the past, you won't need to spend a lot of time on beating the game. If you only care about finishing the main storyline, then be prepared to spend about 50-60 hours. If you also plan on completing all the side mission, this time may get doubled.
If you are new to this type of game, your NiOh 2 playthrough will take longer. In this case, it may take up to 100 hours to complete the main campaign. If you also decide to complete side missions, this time will increase to 160 hours.