Zuko is the deuteragonist of The Promise and Avatar: The Last Airbender, a secondary hero whose story is intertwined with Aang’s. Zuko is also an anti-hero; unlike Aang, who is an undisputed force for good, Zuko is torn between his dark past as a loyal subject of his evil father and his present role as one of Aang’s closest friends and political allies. He is highly aware of this internal conflict, and it motivates him to ask Aang to make the book’s titular promise. The reasoning he provides for this request—“The Fire Lord’s throne comes with a lot of pressures, and if I’m being honest with myself…I need a safety net. The world needs a safety net. That’s what I need you to be, Aang” (17)—reveals a youthful insecurity in himself and his ability to do the right thing. This is an insecurity that he wrestles with for the duration of the book, so much so that he is shocked when Aang eventually agrees with his conviction that firebenders should not be forced out of Yu Dao, asking, “So I was right, then…?…All along…my decision…was right?” (216). However, as Zuko realizes later, in forcing Aang to make the promise, he was also abdicating responsibility for his own decisions, something that Zuko characteristically does over the course of the novel. His character arc involves not just realizing that his insecurities are misplaced but also that he is accountable for his actions and decisions.

In his new role as the Fire Lord, Zuko faces added responsibilities and expectations that are disproportionate to his youth. Kori Morishita’s anger at Zuko, for example, is founded on the perception that he carries responsibility not only for his own actions but also for the actions of every Fire Lord in his dynasty: “My family has been loyal to yours for generations!,” she tells him, “By getting rid of me, you would simply complete your betrayal” (23). These external pressures heighten the pressure Zuko puts on himself to be good, driving him to seek moral clarity from Ozai, Iroh, and Aang instead of from within himself. Although Zuko shows character flaws, he also shows a strong moral compass and an openness to other perspectives.

Katara, Sokka, and Toph make up the remaining members of Team Avatar who play a major role in The Promise. Though they are secondary characters, primarily involved in supporting Aang’s mission to achieve global harmony, they each have individual storylines that enrich the franchise’s multifaceted portrait of a diverse society. Of the three, Sokka plays the most traditionally secondary role in the story, primarily serving as a support system for Toph as she struggles to successfully teach metalbending. His penchant for lateral thinking, a signature characteristic that was established in the animated series, is what eventually enables Toph to reach a breakthrough with her pupils.

Having discovered metalbending in Season 2, Episode 19 of the animated series, Toph has set up a metalbending academy in the time since the Hundred Year War ended. She is a strict teacher with high expectations for her students and is increasingly frustrated as they continuously fail to bend metal. In the author’s notes, Gene Luen Yang explains that at the time of writing, he was fascinated by the ongoing “Tiger Mom” controversy and that Toph’s teaching style is intentionally akin to the harsh “tiger mother” parenting style outlined in Battle Hymn of the Tiger Mother (136). This tough exterior is contrasted with her vulnerable interior life, when she confides in Sokka, “When I brought Ho Tun, Penga, and the Dark One to this school, I expected them to become metalbenders!…I expected them to be something that they’re not. How is what I’m doing to them different from what my parents did to me?” (136). Toph’s careful consideration of her actions and motives highlights her thoughtful nature, which inspires the loyalty of her students.

Katara, Sokka’s younger sister and Aang’s waterbending teacher, copes with feelings of jealousy and hurt as she and Aang embark on a romantic relationship. The zealous attention given to Aang by members of The Avatar Aang Fan Club very quickly makes Katara feel insecure, a feeling which is not helped by the fans passive aggressively referring to her as “Avatar Aang’s first girlfriend” (96). Underlying these immediate insecurities about the relationship are deeper fears about her future with Aang; as Aang pushes to keep the four nations separate from one another, she wonders, “If the nations have to be separate, what will that mean for us?” (197). With these thoughts, Katara highlights the disadvantages of Aang’s simplistic approach to decolonization by bringing it into a personal sphere. By confiding in Aang about these fears, Katara can help guide him toward a better political solution, maintaining her longstanding role as his closest counsel and ally.

The Morishitas are the mayoral family of Yu Dao, comprised of Mayor Morishita (a Fire Nation citizen), his unnamed wife (an earthbender), and their daughter Kori (an earthbender who is also a Fire Nation citizen). Together, the family is a microcosm of the increasingly multicultural, post-colonial world that Aang and Zuko must guide after the end of the Hundred Year War. As Gene Luen Yang observes in his notes, “Mixed-nation families feature prominently in the diverse world of The Legend of Korra. We foreshadow that here with Kori Morishita, and earthbender who is also a Fire Nation citizen” (65), highlighting how these complexities will continue to play a role in the series. The struggles and nuances of the Morishita family’s existence in this novel anticipate broader struggles and nuances that will occur in the near future of the Avatar Universe.

Katara understands that the Morishitas are forerunners of the world’s multicultural future, comparing the future she imagines with Aang to their life in Yu Dao. She tells Aang, “On our first visit to Yu Dao, when I saw Kori’s family…I also saw our future” (197), alongside a panel illustrating the two of them as adults, still in love. This imagined future normalizes the Morishita family’s existence, creating space in the heretofore deeply culturally divided world for a sharing and blending of cultures. Furthermore, as the Avatar, Aang’s participation in an airbender-waterbender relationship with Katara sends a clear message that cross-cultural intermingling does not have to be perceived as a threat to global harmony.

Avatar Roku is Aang’s predecessor, a firebender who was childhood friends with Fire Lord Sozin, the Fire Lord who started the Hundred Year War. Roku knew of Sozin’s plan for world domination but hesitated to destroy him because of their friendship. Ultimately, Sozin deliberately failed to save Roku from a volcanic explosion on his home island, knowing that the Avatar’s death would enable him to wage war on the other nations unimpeded. Like Aang’s strained friendship with Zuko, Roku’s ruined friendship with Sozin contributes to the theme of Friendship Challenged by Moral and Political Differences.

Since Roku is one of Aang’s many past lives, Aang has access to his spirit and can converse with him whenever he needs counsel. In Avatar, Aang relied heavily on Roku’s advice, learning from his life story that indecision can be a fatal mistake for the Avatar. In The Promise, however, Aang finds that he cannot, in good conscience, listen to Roku’s advice that he should kill Zuko. When Aang tells Roku, “Everything’s so different now. It’s not like when you were alive” (218), he characterizes Roku’s perspective as outdated, signaling that the wisdom of Aang’s past lives may be limited in ways that were not explored during the animated series. Finally, Aang’s solemn decision to permanently sever his connection to Roku indicates that the disagreement between the two Avatars is profound. This extreme difference in perspective demonstrates that the Avatar experiences character development not just over the course of one life but also across lifetimes.