When traveling with the Straw Hats, Vivi had a great amount of respect for Monkey D. Luffy, both as a captain and as her friend, openly showing both amazement and disbelief at his great strength and fighting abilities, which would sometimes make her doubt her own fighting skills and feel the need to show that she can handle herself despite the clear difference in fighting capabilities.
Her high opinion of Luffy did not change when she learned that his father was the world’s worst criminal. Instead, she was concerned for his safety. During the Levely Arc, she openly stated her friendship with Luffy to Rebecca and Shirahoshi.
At first, Shanks never took Luffy seriously because he was just a boy, so he mocked Luffy’s dreams to become a pirate, dubbing him “Anchor”
Shnaks entrusted Luffy with his signature Straw Hat, which is of extreme sentimental value to Shanks (as it belonged to his former captain). There is an understanding between the two that Luffy will return the hat upon him becoming a great pirate, a promise that they have both taken very seriously – Luffy defends the Straw Hat with his life, upon arriving at Marineford, Shanks was not ready to accept the hat back. Benn Beckman told Shanks that Luffy is going to make something of himself, which Shanks confirmed by saying that Luffy reminds him of himself when he was Luffy’s age. Just as Luffy is currently looking for Shanks, Shanks eagerly awaits the day that he meets up with Luffy. Shanks also sees Luffy as the future of piracy and was so delighted at seeing Luffy’s first bounty that he threw a party to celebrate, even though he was already suffering from a hangover from getting drunk previously.
After Luffy’s actions in Charlotte Linlin’s territory was revealed to the world and has marked him as the “Fifth Emperor”, Shanks was pleased with Luffy’s progress and stated that Luffy is almost ready to meet him.
Although he had amnesia for ten years and forgot Luffy and Ace, Sabo regained his memories after Ace’s death. Sabo resolved to protect his remaining brother at all costs.
It is shown that Sabo has gained an overprotective attitude towards Luffy as he held off Admiral Fujitora and told him that should Luffy ever need help, he would be there for him, having refused to ever lose another loved one ever again. He also came to Luffy’s aid when Jesus Burgess attempted to kill Luffy firmly telling the Blackbeard pirate that Luffy is his brother and he has to go through him to get to Luffy.
Upon his departure from Dressrosa, Sabo visited Luffy again and gave the Straw Hats Luffy’s Vivre Card, of which he took a piece, and entrusted Luffy’s well-being into their care similar to what Ace had done.
After he read the newspaper detailing the Straw Hats’ activities in Totto Land, Sabo was so proud of his brother’s achievements that he fell to ground in joy.
Originally antagonistic towards him, Hancock saw Luffy as a man who, being immune to her charms despite seeing her naked, could not be allowed to exist.
Due to Luffy’s bravery, selflessness and kind heart, Hancock has fallen in love with Luffy, causing her to have “Love Sickness”, which was the cause of death of nearly all of the previous Empresses. However, Elder Nyon says that all of the previous Empresses died because they tried to suppress their feelings by distancing themselves from their object of desire, whereas Hancock will survive by going with Luffy.
Due to her feelings, Hancock has a hard time looking Luffy in the eye and tends to blush in his presence (much like a young girl with a crush). She is also prone to daydreams involving Luffy. She continues to tend to faint in joy whenever Luffy says her name right and apparently is keeping count of how many times he has said her name correctly. When Luffy hugged her during the Battle of Marineford, she thought of it as a proposal of marriage. Later though, Nyon told her that she wasn’t married. As a result, Hancock is now set on the idea of marrying Luffy. Even though Luffy says that he is not going to marry Hancock, she still loves him very much and is not deterred in the slightest by this.
During the Battle of Marineford, Hancock states that all men, both Marine and pirate alike, are her enemies, Luffy standing as the lone exception.
Two years ago, when a stray lightning bolt saved Luffy from being executed, Bartolomeo was in the crowd and was amazed by the spectacle. He followed all of the news about Luffy and the rest of his crew, up until the war at Marineford, which inspired him to quit as the head of the mafia he ran and start a life of piracy. He even traveled to Dressrosa for the sole reason to acquire the Mera Mera no Mi to give to Luffy as a present. After his Block B fight, Bartolomeo heard a man criticize Luffy. Bartolomeo proceeded to scold the man and cut off his tongue, portraying the severity of Bartolomeo’s obsession and respect of Luffy.
Bartolomeo sincerely believes that Luffy will become the next Pirate King.
When he met Luffy, he could barely speak and fainted multiple times.
After the Dressrosa incident in which Luffy defeated Doflamingo, Bartolomeo was among the seven representatives to swear fealty to Luffy and the Straw Hat Pirates, under the Straw Hat Grand Fleet.