Damien is one of the protagonist's main rivals, along with Eva. Like the player, he is on a Pokémon adventure of his own. He appears across the region, either challenging the player to battles or teaming up with them in times of crisis. Damien is part of the friendship system, meaning that the ways in which the player decides to interact with him (and with Eva) will affect his role in the story.
Damien is far less concerned with filling the Pokédex and much more focused on the trends of Vereshad and the Pokémon training community as a whole. Although he aspires to be a trend-setter, Damien is more of a follower; he regularly switches up his looks and Pokémon team to follow what he perceives to be the wave of coolness. Although he tries to come off as uncaring about what other people think, Damien's desperation for social approval is fairly obvious to those around him. Eva frequently mocks Damien's latest trend-following blunder whenever they meet, although he only seems to take genuine offense if the player agrees with her. If the player is closer friends with Eva than with Damien, he will go out of his way to get their attention and social approval.
Beneath the needlessly expensive clothes, Damien shares a genuine love for Pokémon battling with the protagonist and Eva. He is fussy about making sure his Pokémon are taken care of and happy, which translates into a somewhat nursing attitude directed towards those he cares about. Whether the player will see this side of him depends upon how strong their friendship with him is.
Damien lives with his grandma, grandpa, and little brother. The protagonist will find out more about his family life, goals, and personal struggles with a high friendship. If the player views his trainer card, it is possible to see that Damien's name is actually David. He "changed" it to Damien because it "sounded cooler" by scribbling over his old name with a pen.
Damien is part of the friendship system, so his relationship with the protagonist is influenced by the player's in-game dialogue choices.
Damien has known the protagonist since they were kids together in Cadere Town, although they were not close as children. He has always felt that the protagonist's family was a bit weird due to their constant competition with each other. Damien cannot relate to that family dynamic since his family has always been extremely loving and supportive of both him and his younger brother. Damien's friendship with the protagonist can develop more depending on the player's choices.
Damien met Eva when she first arrived in Cadere Town to meet with Professor Sakura. He sees Eva as his friend since she did not have any besides Professor Sakura in Vereshad. Damien values her input on his training techniques even though he verbally brushes them aside. He constantly tries to impress her and show his worth as a "cool guy" from Vereshad to boost his own ego. Damien enjoys teasing Eva when she does not understand a Vereshad custom or phrase. He believes her colder personality is just that and does not take offense when she is short with him. Damien feels genuinely hurt when he does not see her approval of him. His relationship with Eva can change in the game depending on the protagonist's choices.
Professor Sakura watched Damien grow up over the last decade and wanted to see him become a Pokémon Trainer. The two were close because Damien would follow her around when she was conducting experiments. He originally wanted to become a scientist to work with her, but after watching Professor Sakura for a while, he decided it was "boring" and instead wanted to become a Pokémon trainer.
Damien has known Mariana since they were children in Cadere Town. They did not interact a lot while growing up, but Mariana did help him out when he got into trouble. When he first battles Mariana, he is easily defeated and faces an internal crisis. He questions how anyone could defeat her when she appears so perfect, and he doubts his own skills. He strives to be like her because he views her as trendy and "cool".
Damien has known Martin since they were children in Cadere Town. They did not interact a lot while growing up, and he never felt comfortable around Martin. Martin intimidates Damien, and he views the Gym Leader as a "not cool but tough guy". Damien is confronted with his fear when he faces Martin in the Gym Battle. Although he loses the first three times, Damien is determined to defeat Martin and finally does so on the fourth try. He is shocked when Martin compliments his battle skills.