Kanuto backstory=filler. I don't mean anime filler, i mean wasteless manga chapters that he makes to buy time to think of a new idea.
ok i gotcha. I hated every single kabuto chapter because i was too anxcious to see iznami, but they aren't really fillers. they're character's backstory that you had to understand in order to figure out why iazanami worked. Imagine if there was no explanation from Nagato to Naruto about his past, and he just gave up his life, you'd be like WTF right? Why Kisame killed himself, why Deidara was so desperate to kill Sasuke, Why Sasori didn't kill Chiyo and Sakura ( and yes, for Chiyo fans, she said he saw through the last attack, couldve easily dodged and countered, justthrowing it out there)... there's many more, bt those are a neccesity. I could've gone through my life without knowing Kabuto's backstory, but still.