TL;DR: An all around great read and I'm happy I found it.

This was quite honestly the single most powerful piece this Fandom has to offer. It really raises the bar and I'm glad I stumbled upon this. The fact that you decided to keep Frisk reluctant to fight until the bitter end. The amazing foreshadowing you achieved by establishing early into the story. A real feeling of sibling love between Asrial and Frisk. The dramatic reunion and bitter struggle is described perfectly.

Just... This isn't a fanfiction you just binge-read. This is a well crafted original story that you read, set down, absorb, and think about. Many 'professional' authors can't manage your action parts. The drama actually pulls you in. You feel the anguish the characters feel and you become joyful when they smile.

Also, you managed to keep Frisk's gender questionable! Not once can you tell if they are male or female, effectively doing the one thing no one else has ever managed to do! This honestly deserves all of the recognition possible.

That being said, I do wish that the flower invasion hadn't come so abruptly. Considering the quality of writing, this was perhaps done because it was decided to not be necessary to the plot. Especially when you take into consideration that everything else was well paced. Just one of those things you nitpick because it might later help the writer.

Sans mistrust of Frisk is depressing. I'm not complaining, it just made me feel sad. T.T

Okay, this review has gone on to the point that it's just me literally ranting and raving praise. 5/5 Stars

Also noticed that the hate reviews... seem to be one person spamming like a jerk. The day did not change and getting that much reviews by one day, is nigh impossible, even on mainstream.

What an asshat. Hey! They even admitted it themselves! (Check the earlier reviews of Guest.)

Also noticed that most of those hate reviews seem to be only one person since the time difference is not at all that far apart.

What a jerk. Seriously, an asshat, I might say.

Wow. The guests here really don't have class. The 'actual' users at least, have good taste. ;P

Seriously, though. Great fic! I DID feel it was rushed near the end, but the characterization was fantastic! The end fight didn't feel as stretched out, which was kind of a bummer.

8/10, though! Good job!

Hey.
I haven't even read this story yet, but I'm going to tell you now. Disregard all the guest reviews on this fic. Or at least the first huge stack of them below this one. Some guy had a massive hate-boner for this story and spammed it with bad reviews to hide the good ones. If you want ACTUAL reviews of the story, skip to page two of the review page if you're on mobile (I don't know if it's the same on PC). Once you reach the non-guest reviews, then they are all real.
Decide if you want to read it then.

I’m done. It’s only Chapter 1, but I’m already done. This is... really bad. To the point where I can’t stand it. UGHHHH
Undertale fics are supposed to be GOOD.

Jesus, this is awful. PLEASE tell me you’re joking with the “Chara smile”. Ugh! Either she’s Chara or she’s not Chara. Honestly, I don’t care either way because your writing is so bad I can’t understand the plot most of the time. And I have a Master’s Degree in English Literature!

You’re an AWFUL writer. For anyone scrolling through the reviews to see if this story is good, spoiler: IT’S NOT. It’s really, REALLY bad! It’s like you’re doing this on purpose!
...
...
...
Wait. Are you?
Nah, you’re probably just an awful writer.

Wow. This was REALLY bad.
Tips for being better: Grammar, general plot lines, and just... EVERYTHING.
*shudders*
Now, if you’ll excuse me, I have to take a shower to get the feel of this awful book off of me. :p

PHEW! It’s over... this was the worst story I’ve ever read!

This is terrible this sucks I hate it make it stop make it STOP!
Grammar, plot... everything is terrible.

This is awful. Your writing is awful. YOU are awful.

Wow. This is really bad. I can’t believe that this is just 16 horrible chapters of bad writing. I’m reading them all just to amuse myself.

Suck me
You are the worst
I hate this

Honestly,
You are the worst writer I have ever read. This story is atrocious. It has no plot except something copied from LITERALLY EVERY OTHER FANFICTION IN THE WORLD. This is trash. Never write again, please. It would save us all some misery.