Warning: MAJOR spoilers for Undertale (you know, in case someone exists that doesn't know of the Genocide route at this point, but... better safe than sorry).

AuraWielder Analysis:

I got to thinking recently... as I was listening to this song (which is one of my favorites off of the mostly mediocre "Mobile Orchestra" Owl City album... as crazy as it sounds, this song relates EXTREMELY heavily to Undertale. In particular, to Sans in the Genocide route. Obviously, it wasn't written with Undertale in mind (Mobile Orchestra released in summer 2015 while Undertale was released later in September 2015), but the similarities feel almost deliberate. Let's start with an analysis...

NOTE: While I will say "this part refers to" or something of the sort, I'm not saying that the song was written FOR Undertale in some way, because again, Undertale was released AFTER this song came out. This is to merely point out how it almost perfectly applies to the game.

"So I walk alone down the darkest roads
'Cause I've always known how the story goes"

Having 'I' relate to Sans makes sense regarding him in the Genocide route. "Walk alone" refers to Sans being the sole survivor of the Genocide route's "darkest roads". "I've always known how the story goes" is a reference to Sans' awareness of this "story" of the Genocide route getting played over and over. He is somewhat aware of "resets", "saving", and "loading" and has stopped Flowey in his own Genocide runs.

"When the curtain falls I'll be wearing thin
Clawing at the walls as they're closing in"

General depression and panic within Sans as it's almost impossible for him to understand just WHY and HOW this keeps happening.

"In this twisted plot I was destined for
I'm an astronaut on the ocean floor"

"In this twisted plot I was destined for" is again the "twisted plot" of the Genocide route, and "destined for" means Sans knows how many times he's played the role of stopping the Genocide route over and over again with Flowey.

"So misunderstood 'till the bloody end
How I wish I could do it all again"

General regret over why things have to be this way. He would wish that he himself could "save" and "load" to fix things himself, but he's only aware of the hell he's living, seeing his brother and friends killed multiple times by Flowey.

"It feels like I'm a lone survivor
Forgotten in a dark and deadly world
And on my own I walk alone
To see the sun again I'd give anything"

Again, Sans "walks alone" on his awareness of "save" and "load" and "resets" other than the genocidal Flowey and Frisk knowing of them. "Lone survivor" would be the fact that, well, he's literally the last living thing standing between Genocide Frisk and his/her completion of the Genocide route and the destruction of everything. "Dark and deadly world" is again, the Genocide route.

"But life demands a final chapter
A story that we all must leave behind
It's do or die, and this is mine
The anthem of a bird with a broken wing"

Win or lose, Sans will still do his damndest to not let that destruction happen. Even though it may be his "final chapter", he knows that this is "do or die" time for him, hence why he becomes serious and the hardest boss in the game.

There's a few repeats of the verses and chorus until the final verse comes into play...

"Tell the world I know that my mind is made
It's a horror show, but I'm not afraid"

Sans is NOT afraid of the "horror show" that Genocide/potentially possessed by Chara Frisk has committed. His mind is made up to stand in his way again and again and again... no matter how many times Frisk resets to a loss.

"Though I won't be missed, I would say it's time
For a different twist in the storyline"

The final lyrics and perhaps most significant. "won't be missed" means that nobody is going to know how he stood up to Flowey and Evil Frisk countless times, singlehandedly stopping the destruction of the Undertale universe. This "different twist in the storyline" lyric means that he's going to keep beating and beating and beating Frisk until THE PLAYER gets frustrated enough to reset the game and restore the characters and monsters back to their original status, knowing that's his only shot to 'win'.

So yeah, it's obviously not intentional on the song's part, but it's almost DAMN uncanny how this song relates to Sans in the Genocide route.