Here’s a short summary of why I think Deltarune’s narrator is Chara - Undertale’s Chara.
In the vessel creation sequence, there are two speakers - Gaster, and a mysterious second person…
…who just so happens to talk exactly like Chara does. (read here for more in-depth explanation on the language differences).
Also, the final update for Undertale on PC added many Deltarune-related hints…
Clamgirl says the time we would meet Suzy was “fast approaching”
Clamgirl turns into a grey Gaster follower
A drawing of three smiling people saying “don’t forget” appears after this
And there was also this message added, found only in the strings:
This also matches Chara’s speaking style. And it seems like they may have been talking to Gaster, which explains their presence in the Vessel Creation Sequence.
Now If Chara is in Deltarune’s universe working for Gaster on a plan - as is implied here - why would they not reprise their narrator role?
Why would they not take the opportunity to keep the closest eye on the action they can? Or, to ensure the plan is kept on track, and on schedule?
…in spite of one chaotic teenager who would probably really like to waste time?
…or, perhaps, even, to occasionally be very judgy towards that teenager and gently make fun of them?
…but still find it in them to be touched when that teenager gives Asgore food for his fridge?
…to extol the virtues of chocolate?
…and be very weird and cagey any time the mysterious Man shows up?
There’s a lot to say about the narrator that’ll need a much longer post, but I think the signs point to it being Chara - the same one who narrated for Frisk in Undertale.
