"Shikamaru's Analysis!!" (シカマルの分析!!, Shikamaru no Bunseki!!) is chapter 324 of the original Naruto manga.
With Hidan in his transformed state, Asuma finds that all the damage he does to Hidan is also done to him. This also applies to damage that Hidan does to himself, a fact he takes advantage of by stabbing himself to immobilise Asuma. He tries to stab himself in the heart to finish of Asuma, but is caught and stopped by Shikamaru's shadow. While straining to keep Hidan from finishing his attack, Shikamaru analyses his actions and discovers how Hidan has linked himself with Asuma.