Madara saw how often he looked at his wrist; that

bastard

. He watched Tobirama when the idiot thought no one was looking, how his eyes would fall to his wrist and he would bring his other hand up to draw a thumb across the mark there.

It was disgusting. It was shameful. It was less than Izuna had deserved. Madara scowled as he watched the Senju trace each letter with care, his own clan name in black ink. He was very aware that murderous waste of space had no idea who the writing was meant for, just as Izuna had never had the chance to discover who his writing was for. It wasn 't until he had worked side by side with the Senju, saw his signature on form after form, that he realized. Only then had he looked at the bastard 's wrist and seen it for what it was.

His brother 's handwriting on the hand that had murdered him.