An often underrated character from Naruto, Mizuki was probably one of the greatest geniuses in the Naruto manga. Despite being "only" an academy teacher, he was capable of keeping the rest of the village in the dark as he secretly planned on stealing the important scroll of forbidden jutsu right from under the Hokage's nose. While everyone shunned Naruto, and only saw him as the reincarnated demon fox, Mizuki saw an opportunity. The other ninja and villagers refused to acknowledge Naruto’s existence and thus he could move around undetected, the perfect tool for Mizuki's machinations. But that wasn't the only trump card that Mizuki had when he played Naruto as his hand, for unlike most, he could clearly discern that Naruto was not only ignored by the population, but somehow had a space reserved in the heart of the current Hokage--Sarutobi Hiruzen. With this knowledge in hand, it was clear that his plan would go without a hitch as Naruto snuck into the Hokage's office and stole the scroll, while disabling the Hokage in the process.
Truly it was insight that surpassed the Byakugan that allowed Mizuki to get as far as he did, he even managed to create an opening in Konoha's barrier through which Naruto snuck out of the village into the surrounding forest to a place that no one knew of. It would have worked perfectly had Iruka not happened upon the secret area by chance. Dumb blind luck on Iruka's part is the only reason that Mizuki didn't get away with stealing the scroll, despite being in the Hokage's office, in the centre of the most powerful village in the word. Truly, Mizuki was an unrecognized genius.