The rare moments where they were alone- no matter where they were- in which Zoro knew something bothered his captain, the only thing he would do was be there beside him, giving him the strength he, somehow, knew the other needed.
"Hey, Zoro." The green haired man's eyes turned towards him. He didn't need to ask, Luffy knew he had his full attention, "I'm glad to have you with me." And that grin was enough to almost, almost, bring a smile on the Pirate Hunter's lips, instead he just groaned and his hand rubbed the other's head over his straw hat.
"Mind your business, Captain," Zoro answered, making Luffy's grin become even wider.
Were those moments the ones they cherished, enjoyed. In the silence of the guard's nest, at ungodly hours of the night while in vigilance duty. Luffy used to climb there just to 'keep him company' even though he didn't need it.