'Yakushi Kabuto is a first-rate spy.' In which Itachi admits that he's emotionally retarded, and muses on Kabuto's ability to hide his emotions. Spoilers for Chapter 289 and up.
Yakushi Kabuto is a first-rate spy.
This Uchiha Itachi knows, and knows very well. Kabuto was only a year younger than him, but he manages to hide every emotion of his behind a bland, careless smile. Itachi knows his weaknesses, and isn't afraid to admit them. His sole flaw, if it can be considered a flaw at all, is the fact that he is utterly unable to conceal any emotion that he has.
The only reason that it isn't his downfall is the fact that Itachi doesn't have many emotions at all.
Uchiha Itachi likes to watch Yakushi Kabuto, especially when the white-haired man meets Sasori in front of all of the Akatsuki members. Itachi had realized long ago that Kabuto is hiding something from his so-called 'master', but Kabuto is always hiding, concealing his true self behind a perfect smile and a subservient tone
Itachi knew that Yakushi Kabuto cannot be trusted, and that he will betray Akatsuki sooner or later. Or perhaps Yakushi Kabuto cannot be trusted, because one day, he'll bring Orochimaru's head in front of the Akatsuki and flaunt it in their faces. Itachi cannot see which outcome it will be, because Yakushi Kabuto is the only person that Uchiha Itachi cannot read.
People are rather like books, Itachi knows. Every single person is a totally different book. Kisame is a classic, beautifully written novel with a red leather-bound cover and horrendous cover art. Orochimaru is an old scroll full of kinjutsu that will break apart in your hands if you aren't careful enough. Sasori is one of those books that Shisui had told Itachi of, once upon a time. Sasori is a book that, when opened, swallows souls and holds them captive until the end of time. Deidara is an art lover's book, full of colorful illustrations and simple instructions. Deidara is a simple person.
Yakushi Kabuto is an ancient diary discovered in a forgotten attic of an abandoned house, plain and unassuming and locked with a heavy lock without a key. Itachi wants to find the key, because Itachi dislikes not being able to read people. His Sharingan allows him to read even the best shinobi like an open book, and yet this /boy/...
Uchiha Itachi knows that Yakushi Kabuto will betray Akatsuki one day, or he will exceed all of their expectations and bring them Orochimaru's head when no one else has managed to even touch a hair of Orochimaru's head before. Itachi doesn't know which outcome will happen, and he can't see the future of this white-haired Orochimaru-spy. He can't open the lock.
But he continues to try. It's becoming a hobby, of sorts, to try to pry open the lock of that diary whenever that diary enters his thoughts. Itachi doesn't know why he tries, because it's likely that the diary probably contains a lot of useless information.
However, Uchiha Itachi knows that Yakushi Kabuto is the only person who knows how to hide every emotion he has inside a fake smile. And Itachi wants to learn how to. Itachi wants to learn how to hide every emotion that does appear, just so that he can eliminate this weakness of his.
It won't do if he dies before Sasuke kills him, after all.