XIII機関
After "Kingdom Hearts II Final Mix" was released, Nomura wanted to expand Roxas' role in the series to explain the events between his birth and his disappearance from Organization XIII. For "Kingdom Hearts 358/2 Days", the staff thought that Roxas' role as a member of the group would be a suitable theme for the plot. Roxas was chosen as the game's protagonist as the staff thought that having a main character besides Sora would help to introduce gamers to the series' first Nintendo DS title. Co-director Tomohiro Hasegawa explained that Roxas' was originally shorter, and the staff decided he should grow taller as the game continued to develop. Nomura wanted to portray Roxas' activities differently from Sora's. In Sora's games, he is on a journey around the world, while Roxas always returns to Organization XIII after each mission. The staff constructed Roxas' interactions with the Disney characters differently from Sora's, as the Organization was meant to be secret in the game's story. Nomura told the writers that he wanted Roxas to learn something from each of his missions or just to have something to think about. Nomura later clarified that Roxas' personality was different from the one portrayed in "Kingdom Hearts II", as he does not actively attempt to come into contact with other characters. With "Kingdom Hearts 358/2 Days", Nomura wanted to reveal why Roxas left Organization XIII. Although Nomura found it a sad story, he considered Zack Fair's ending in "" to be more tragic. Nomura felt Roxas' last words in the game were also the title's most significant, as he wanted them to connect to "Kingdom Hearts II"s first scene, which is actually the same scene. Uchiyama expressed sadness when the game's development ended as he would not play the character for a long time.