Board Thread:Questions and Answers/@comment-26090671-20160919083446/@comment-27701762-20160920052219

It doesn't really make sense for it to be anyone but Asriel.

In order for it to be Chara, there are two possibilities for how Chara fits in: 1) Chara is the narrator following Frisk around through the Underground. 2) Chara is simply a wandering spirit trapped in the Underground. In case (1), Chara would be narrating to Frisk about the need to save Chara. So Chara is talking about themself. But since A) it is already shown that the characters absorbed by Asriel essentially lose all sense of hope, whereas the narration doesn't change in any way, and B) the narrator talking about themself should be signaled in some way, perhaps by saying how Frisk is saving "Me" (i.e. Chara), it doesn't make any sense for Chara to be the narrator and also be absorbed by Asriel. We could get around the problem by assuming that Chara is not the narrator and going with case (2), but in that event there is no reason that Frisk would know who Chara is or how to reach out to them, so it still would not make sense.

In contrast, the line specifically says that there is "one last person" to save. After first hitting the "Someone else" SAVE, the SAVE changes to "Asriel." If "someone else" is Chara, then there are two people to be saved, not one. So it makes more sense for it to be Asriel given the immediately preceding line.

Meanwhile, your concerns about the narration playing coy are perfectly in line with drawing out a sense of dramatic tension. Since the second half of the fight is supposed to be an uplifting scene where Frisk saves their friends, the culmination of it should end with Frisk defeating the final boss by "saving" them (to also provide a cap to the overall point of the game, which is that enemies don't need to be defeated through violence). The narration's ambiguity is simply playing up the reveal that you can defeat Asriel by saving him. The scene it shows is Asriel coming upon Chara and taking them back to his parents, reminding him of who he once was (something needed in order to save him, as was shown in the preceding parts of the battle).

The narration is ambiguous to make the final moment all the more powerful for the person experiencing it in the moment. There is no way that "someone else" could be Chara or any other character without making the rest of the scene senseless.