Rysangel
harem usually ruins the story, I wouldn't mind if there is harem after 4th ninja war but adding harem before that will likely not help the story. its better to focus on teacher-student aspect while mc is preparing for future. gor example, he can steal uzumaki mask, plan to kidnap karn, etc. aka use future knowledge and not just focus on teaching or interaction with other ninjas
pleaee. if you want to make it as a harem story. PLEASE make it reliable harem story. not just every time sanada meet a canon female character, passively he make them his harem. please! dont make this story feels like the other "harem self fulfilment" story. i know it is just a fanfic. but that not mean a fanfic can not become a realy good story.