The manga and anime series One Piece has Trafalgar D. Water Law and Monkey D. Luffy as two of the most popular characters. Their relationship, though not by blood, is very well developed through the course of the story and forms one of the main features of the storyline.
Initial Encounter and the Formation of an Alliance
The first time Luffy and Law met was in the Sabaody Archipelago, although at that point, their interaction was very minor. The change in their real relationship came during the Marineford War, where, for reasons unclear at the time, Law ultimately decided to save Luffy's life after the battle. It is by his action of saving Luffy that their complicated relationship really began.
With these events finally over, Law offered to form an alliance with Luffy and the Straw Hat Pirates. This alliance was supposedly to overthrow one of the Four Emperors, Kaido. Luffy agreed to this offer thus formally allying their crews.
Nature of Their Alliance
The nature of Luffy and Law's alliance is a point many fans, and even the story, seem to debate. From Law's point of view, it was like an availability-based deal concerning the achievement of certain goals. He looks at it from a more strategic point of view in terms of partnership rather than a friendship.
However, to Luffy, this alliance is more or less a friendship due to his naive and friendly personality. This results in tension and some really comedic moments between the two at times because of their differing perception.
Development of Their Relationship
This development of the relationship between Luffy and Law is more evident, most especially in the Dressrosa and Wano arcs. Though at the beginning, Law was trying to make the alliance strictly business, Luffy's nature and all their experiences bond them closer.
Law has become very devoted to Luffy, even going so far as to put himself in harm's way for the sake of Luffy's ambitions. This can be highly noted in the fight against Doflamingo, when he was willing to die for Luffy's sake.
Dynamics with Other Characters
Considering their relationship, a lot of times this is contrasted with Luffy's interaction with other characters, particularly Eustass Kid. While Luffy and Kid get along in a more abrasive and competitive way, Law tends to be more tolerant of Luffy's chaotic nature.
He has also developed relations with other Straw Hat crew members, namely Chopper and Robin. These bonds reinforce even more the relationship between the Heart Pirates and the Straw Hat Pirates.
Story Impact
The alliance of Luffy and Law has been an influencing factor throughout the storyline of One Piece. By joining forces, they have made huge waves in the plot, taking down Doflamingo and now standing against Kaido and Big Mom.
Their relationship also reflects an even greater theme in One Piece: the power of alliances and friendship with which one can conquer obstacles that, alone, seem insuperable. Their pairing has been formidable despite differing approaches and personality traits.