Board Thread:Naruto Discussions/@comment-24120130-20140725123237/@comment-24531362-20140827083651

JOA20 wrote:

Well, Kabuto stated that Orochimaru found the source of Jugo's power in the Ryuchi Cave. Not that all senjutsu comes from there.

Logic map time!

1. Kabuto knows, through access to Orochimaru's notes, that Jugo possesses a form of passive senjutsu chakra generation Kekkei Genkai.

2. Orochimaru sought out the snakes of Ryuchi Cave to learn senjutsu, and was partially successful.

3. Building off Orochimaru's notes, Kabuto also learns senjutsu in Ryuchi Cave.

4. It is unknown whether Orochimaru was aware of the toad sages of Mt. Myoboku, or if he recorded such information in his notes, as it would be of no consequence as he could not access Sage Mode himself in the first place.

5. If Orochimaru didn't know something, it is likely Kabuto didn't either.

6. Therefore, it is possible that, possessed of only the knowledge we know for a fact that he had (Ryuchi Cave, Jugo, Orochimaru, and Senjutsu) that Kabuto may have assumed that all senjutsu somehow came from Ryuchi Cave, including that of Jugo.