Board Thread:Questions and Answers/@comment-9826910-20130618064245/@comment-10630156-20130618091444

Zangetsu is the name of his real zanpakuto and that is hollow ichigo

It appears that the person we know as Zangetsu was a fake the entire time and that he was suppressing most of Ichigo's latent potential as a shinigami and he is Ichigo's inner quincy hence why he appears like yhwach did 1000 years ago (about the time the quincy were made apparently). The shinigami powers that Ichigo has possessed until now is the fraction of power 'yhwachZangetsu' couldn't suppress in other words Ichigo has a whole lotta power he has not been able to use up until now that he can use. Hollow Ichigo did say once 'I am Zangetsu' to Ichigo and along with his complex towards Ichigo calling him 'partner' or 'your majesty' and saving his life when he is in danger even though he is part hollow most of his inner nature seems to be that of an Zanpakuto which makes sense seeings that he is one. the old man (Zangetsu) was origonally going to kill Ichigo but after seeing him work so hard he decided against it and helped him instead using his real zanpakuto (Hollow Ichigo) as a teaching tool of some sort sending it away when its job was done which is why Hollow Ichigo kept on vanishing right after he'd taught a lesson to Ichigo and reappears when another is to be taught.