The Guidepost of Reunion (再会の道標, Saikai no Michishirube) is chapter 576 of the Naruto manga.
After Sasuke spots Itachi, he chases his brother down. Itachi refuses to be swayed from his mission, so Sasuke attempts to use Susanoo to stop him, but Itachi counters with his own. While Sasuke chases his brother the two have a conversation. Elsewhere, a regenerating Madara decides to target Tsunade after realising she was a Senju. Deeming her a weak woman who had seemingly inherited nothing from Hashirama who he claimed was even more skilled in medical ninjutsu than she was, he goes on to say that even more so that a weak person, he detested a weak Senju. Tsunade however rebuffs him, telling him that though she had not inherited the Wood Release kekkei genkai her grandfather possessed and that he may have even been more skilled than her with medical ninjutsu — since he did not require the use of hand seals to use it, Madara made two mistakes. One was assuming she was a weak woman and the other was that she had inherited nothing from her ancestor. She states that she inherited something more than simple power, the Will of Fire — something Madara should not take so lightly.