Considering how strong Spiral Zetsu is, I wondered why Kishi would wait so long to bring him out as a weapon. I mean he's using wood release on SM Hashirama's level, you would think a trump card like that would be used by Obito before he got defeated? After thinking about it, the only conclusion I can come to is that Spiral Zetsu was not at all loyal to Obito at all. He must have stayed hidden ever since Obito took over, perhaps by convincing Obito he died at some point to help him escape his detection.
Either way, there is no way Spiral Zetsu was still loyal to Obito or he would have been helping in the fight long before this. I think its clear that Spiral Zetsu is loyal only to Madara and only showed himself now because his strength is making the fight lean greatly in Madara's favor.
Either way, there is no way Spiral Zetsu was still loyal to Obito or he would have been helping in the fight long before this. I think its clear that Spiral Zetsu is loyal only to Madara and only showed himself now because his strength is making the fight lean greatly in Madara's favor.