With the completion of the Core, some monsters had decided to leave Home behind and live in the biomes of the cave that aligned more with each individual's needs. The war was nothing but a distant memory to most of the monsters, so the fear of outside threats faded overtime. 

There was still this lingering wariness in the air, which was kept alive by the warnings and stories from the older generations, but it was long not enough to keep anyone hidden in the deepest part of the cave. 

Just like how it appeared humans forgot about the existence of monsters, monsters would have almost forgotten about the existence of humans if it weren't for the stories and the fact that a human was living among them for decades. Not only that, but that very human acted as a guardian of some sort, standing next to the most important authorities in the kingdom. And with you showing kindness every day and having such a big heart, how can humans on the surface be anything like the stories that the elders have told everyone about? 

Not everyone was willing to leave, but slowly the first small community was founded in the snow biome of the cave. As always, Asgore wasn't exactly great with the name giving but now monsters had a small town called Snowdin. The other areas received the names Waterfall and Hotland. 

To prevent monsters from getting hurt or being endangered in any way, Gaster attempted to install security mechanisms and construct an enclosure which only a selected few could enter to keep monsters away from the barrier for safety.

Currently, you were skimming through the bookshelves in Gaster's laboratory while he prepared the next test to determine your soul properties. You both had found common ground in regard of how far Gaster is willing to go while you still were able to help with the barrier problem through his research. Gaster only conducted the most harmless experiments, and you were more than okay with that. 

"No way, I haven't seen this one in ages!", you exclaimed as you pulled out an old and dusty book. You brushed off the dust and carefully opened it. It was the book that Gaster wrote for Toriel and Asgore to explain a skeleton's nature and their sign language. This must be the original one he drafted first. It was handwritten, some parts were scratched out and rewritten. 

"I learned sign language with it." 

'Yes, and you were hilariously bad at it.', Gaster signed and smiled at you. You pouted in response: "Hey! I did quite alright, thank you very much." 

Gaster just laughed and took the book from your hands: 'I put my heart and my soul into this just so people could learn about me...since I am the last one left...It was not just for Asgore and Toriel, it was also to make sure I know where I come from and don't forget who I am.' 

He flicked through the pages, lost in thought. 

'When I first saw you with that book in your hands in the palace, I was furious. I hated the idea of you touching what is basically my very being and all that is left of my species.' You nodded in understanding. Back then, things were really difficult for the both of you. 

'I hated how you spent hours reading through this book with...such curiosity in your eyes.'

'But it made me realize that we are not so different after all. You were just as curious about the world as me.' Gaster smiled at you weakly. 'And when I saw you at that table, signing all the different signs to yourself...at first, I couldn't stand it but when I watched you closer, and saw you struggle with some signs, I just wanted to help. I was somewhat grateful that someone who I gave so much hate, still tried to understand. Meeting you...and getting to talk to you is the best thing that happened to me in my life.' 

"I am also very happy that I got to become friends with you." 'No, you don't understand.' Gaster closed the book and put it back in the bookshelf. He walked up to you and took your hand in his: 'You are more than just a friend to me, [Y/N]. I-' 

His eyes glowed in a hue of pink and he averted his eyes, looking onto the ground instead. You felt your heartbeat quicken and couldn't help but blush slightly. His hand felt so smooth and warm and just know you kind of realized how close you both were. You could practically feel his breath against your skin.

A sudden beeping broke the tension between you, and you flinched. Gaster immediately turned away and rushed to the machine, pressing various buttons. He waved at you to come over. 

"I guess it is time to get to the tests.", you said and walked towards him, mentally preparing yourself for whatever comes next.

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After the experiment, Gaster was occupied once again reviewing results and analyzing the new data sets that you have provided to him. You quietly sat at the table, watching him. 

"Hey, G..." Gaster perked up to look at you. "I have a little surprise for you." 

'Oh? What is it?' You hop off the chair: "That's the thing. It is not here. You wanna go out?" You head towards the door, looking over your shoulder to see if he was following you. Gaster put away his pencil and nodded. He scurried to the door. You grabbed his hand, leading him outside and then to Waterfall. 

'What are we doing here?', he asks, visibly confused. "You will see soon enough." 

You lead him to a waterfall, slowly walking behind it. The droplets of the splashing water gently hit your skin and you can't help but shiver a little at the cold sensation. You approach a set of rocks, occasionally glancing behind you to make sure that Gaster is keeping up. You finally reach your destination, a small crack in the wall which was safely hidden behind the rocks. 

"Come on, in here.", you wave in excitement and crawl through the gap. Gaster hesitates but follows, his eye glowing curiously and illuminating the crawl space. After a few meters of walking, you reach the end of the tunnel. You stand up and stretch a little, then step away to give Gaster some space. 

As soon as Gaster's eyes adjusted to the light, he looks around in awe. You were on a small clearing which was surrounded by waterfalls. The grass had a blue-greenish color, swaying back and forth peacefully and several flowers were scattered across the ground in patches. 

'[Y/N], how did you find this place?', he asks, still absolutely in awe with the view. You shrug: "Well, you come across a lot of different things when you're out for training. Do you like it though?" Gaster nods and you smile in response. 

"I thought this would be a great place for you to retreat to. To think about things and maybe take a breather from work from time to time." You slowly walk to one of the flowers and kneel next to them. You quietly motion Gaster to come over and he sits down next to you. As you touch the flower petals, your voice rings out: "You're doing great and I believe in you, G... Just please look after yourself." 

Gaster smiles at the flower for a moment, then you both get up again and bring a little distance between the flower and you. 

'You did all of this...for me?', he signs in disbelief. You nod happily: "Of course. I thought there is no better way to give you emotional support than through Echo flowers. Almost each one of them has a different message, so you can explore the fields all you want. Thought that would keep it more interesting."

Gaster suddenly wraps his arms around you and pulls you into a tight embrace. He buries his face in your shoulder, tightening the grip around you. 

'[Y/N], you have no idea how incredibly happy you make me...', he signed with his floating hands. 'What would I do without you..?' 

You gently rub his back: "Hey, don't sweat it. I gladly help you wherever and whenever I can." Gaster pulls away and looks into your eyes, his own iris flickering in a gentle hue of pink. 

'Can I...tell you something?', he signs slowly. "Of course, always." Gaster takes a deep breath and looks at you with an unreadable emotion. His iris starts flickering more furiously in a couple of different colors.

'[Y/N]...we know each other for centuries now and you have not only been my lab partner, you have been my emotional support, my calm in the storm...my best friend. I wasn't entirely sure first what these emotions were, because, as you know, I am sometimes not exactly in touch with my feelings but with everything we have been through, things have just gotten clearer and clearer. I spent almost every day of my life with you and I don't think I would still be here if it wasn't because of you. I-'

Gaster looks away, seemingly trying to find the words. Then he looks back at you, his hands trembling slightly as he continues to sign:

'What I am trying to tell you right now...is that, I found myself feeling more for you than just friends. I have fallen for you, [Y/N] and...I hope I don't ruin everything with this now. I-' 

He stops again. 

'[Y/N], I love you.' 

Your heart feels as if it just stopped for a moment and a faint blush creeps across your cheeks. He loves you? Gaster really loves you? You couldn't believe it at first but now you finally heard the three words that you have been desperately wanting to hear from him the past two years.

'With everything that has been going on and what happened to you, I realized how uncertain the future is and I just don't want to have regrets by denying my feelings until it is too late. I missed so many opportunities and I made so many wrong choices. I just hope with you, I didn't this time.' 

Gaster looks at you with a sincere and almost hopeful look, fiddling nervously with the end of his scarf.

"G...I-" Overwhelmed by your own feelings, your breath gets caught in your chest for a moment. You try to calm yourself, almost beaming at him as you finally give him your answer: 

"I love you too."

Gaster looks at you with surprise for a moment, then immediately embraces you. He was almost shaking as all the tension inside of his body seemed to slowly fade. 

He strokes your hair gently, running his fingertips through it lovingly. His other hand glides down your arm and intertwines with your fingers. You remain like this for a moment until Gaster suddenly presses his face against your cheek as if it were a kiss. 

The sensation makes your skin tingle for a moment and another small blush appears on your cheeks. Gaster smiles and looks at your blush, moving his hand from your head to your cheek and stroking it gently. 

'You are absolutely beautiful, [Y/N].' 

You look into his eyes as he slowly leans in. A second later, he pressed a small but gentle kiss against your lips. You kiss back and smile at him. 

Gaster takes it as a sign and kisses you again, this time a little longer and more confidently. 

His hand squeezes yours gently as if he was reassuring you that he had you and would never let go of you. 

After a few moments, he pulled away, still having a happy and somewhat content expression on his face.

'I love you, [Y/N].', he signs again.

"I love you too, G.."

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Unbeknownst to both of you, one of the Echo flowers listened, keeping this memory on record for all eternity.