You are right, I am a big Undertale/Deltarune fan and I'm not surprised that its influence shows in my writing.
In particular, I just love the phrase "despite everything, it's still you" as an encapsulation of how trauma (or life in general) might shape us, but it doesn't have to change who we are at our core.
We don't have to lose ourselves to our struggles. Just because the MC learns they are fae or makes certain choices, doesn't mean they aren't still the same person.
So you clocked that connection correctly, for sure!
(Though the name Az'Lean has no connection to Asriel, that one's just coincidence.)