David Kawena is Nani's boyfriend. David is a great surfer. Like Nani, he also has trouble finding employment. He is also the only one of the four humans (the other three being Victoria, Cobra Bubbles, and later Mertle) aside from Lilo's family who is aware of the aliens and experiments.
Lilo & Stitch
Nani first meets David who gives her a new job at the beach. He then encourages Nani to take Lilo surfing with them to improve their mood. He and Nani have fun together, along with Lilo and Stitch, throughout the movie, and become great friends by the end of the film.
Stitch! The Movie
David is closer to Nani in Stitch! The Movie, though they have not officially dated yet. His role is also smaller here. When he considers the outing with Nani a date, she tells him that she doesn't think she's ready for an actual date. Later, David finds out from Lilo that Jumba was kidnapped by Gantu, to which he inquires, "The Big Dummy?", repeating what Lilo calls Gantu herself. When Lilo and Stitch go on a mission to rescue Jumba and the Experiments, David is not seen again until the very end the film.
Lilo & Stitch: The Series
David has an even smaller role in the series, although he does make several appearences in certain episodes. In one episode, when he convinces Nani to go on a date, he is pecked by Hunkahunka (one of Stitch's cousins) and temporarily falls for some other woman.
In another episode, he teaches Lilo the meaning of Yin and Yang when she and Stitch have trouble working together. However, after two experiments get activated at the same time, Lilo and Stitch eventually team up and successfully capture both experiments, which they name Yin and Yang. After they were rehabilitated, Yin and Yang were seen working together to build a whole new island, and David was impressed when Lilo learned the meaning of Yin and Yang.
Stitch Has a Glitch
David appears in Stitch Has a Glitch in which he tries numerous times to date Nani. However, Pleakley keeps interfering by trying to woo David himself (while dressed as a girl). David later is seen riding with Nani when Stitch runs away, due to his glitch, and mourning over Stitch's apparent death with the others. When Lilo's tears revive Stitch, David and the others cheer. He is last seen dancing the hula with Nani and the others. Nani briefly plants a kiss on David's cheek, much to his astonishment. He then smiles.
Leroy & Stitch
David is only seen at the end of the film when Lilo takes a picture of her whole Ohana (including all of Stitch's cousins from the series).