Random thought, but Might Guy's dad created the 8 Gates, right? Was it ever actually explained how he figured that out? Because it suddenly struck me as kind of weird that none of the OCULAR JUTSU clans seemed to be aware of them despite having varying degrees of enhanced detection of chakra output, hell before Lee's fight with Gaara it seems like Kakashi was the only other person besides Guy and Lee that knew that they existed at all.
