Sacred marriage rope (red silk around pale wrists)

Senju Tobirama allows little Uchiha Kagami to “capture” him solely to taunt Uchiha Izuna with the knowledge that a literal child succeeded in an endeavor he never managed. Only, it seems the red silk rope that radiates Uchiha Madara’s chakra has cultural significance to the Uchiha of which Tobirama is unaware.