When it comes to bonds, whether they are of family or crew, a silent pact is made. As children it was sharing drinks, as a crew member it's stating that you will follow your captain no matter where they lead you, but what kind of pact is made between two lovers? The common answer would be of a sexual kind, but what if that was not something they wished to do? There is a bond between them, but there is nothing to seal it. That is when blood is shared.
Luffy takes the tip of Zoro's sword and slowly drags it across his hand. Not too deep, but just enough that blood starts to trickle down his wrist. Holding his hand up with a grin Luffy held out the sword with the other.
"Your turn, Zoro."
With a silent nod Zoro took his sword and did the same except instead of a grin he only showed concentration as he drew the blade across his hand. Now both hands were bleeding, wrists lined with blood, but none of that matter for this was their choice.
Blood on blood they took their hands into each other's. A seal was made. One another had each other become a part of them. Zoro tugged to bring Luffy closer to him, still hand in hand with blood intermingling, as the softest kiss was given.
"Wherever you go, Luffy, I'll be by your side."
Another kiss was had, but this time playful and quick from Luffy with his hand giving Zoro's a squeeze. The mixed blood continued to seep from their cuts as Luffy grinned even more.
"And wherever I go I'll always have you"
The deed was done. A sealed bond was created out of a red stream of blood and their devotion to forever be the link that connects them together.