S/O has dementia for years, but one day, they don't recognize the skeleton they are married with for 20+ years. For the main boys, and maybe the Horror boys?
Undertale Sans - Sans takes a deep breath, trying to hide how hurt he is. He forces a smile, screaming in his head to not break apart now, and simply reminds them who he is, nervous. He knew it was coming, but he's not sure if he can deal with this. One of Sans' worst fears is to be forgotten in the dark, and well, after so many years, he didn't know he would still have to deal with these old demons.
Undertale Papyrus - He keeps smiling and talking like nothing happened, ignoring the growing pain in his chest. You need support. You don't need to watch him break into pieces right now. Nope. Papyrus waits to go home for this. He locks himself in his closet and cries all night there, as it's becoming harder and harder. He could deal with his S/O forgetting little things, but forgetting people? It's just cruel, and it's hurting so bad. He wants things to be easier like they used to. But he'll be there until the end. He doesn't want to give up just yet. Maybe with that new treatment the doctor talked about? Maybe. He can't lose hope. Not yet.
Underswap Sans - He tenses, really not liking you asking who he is. He sighs, then slowly explains he's their husband, watching in pain as his S/O suddenly remembers and looks at him in pure horror. Blue just hugs them close. It's ok. He's not mad. You don't control it. Besides, it was just one time, no big deal, ok? Blue wants to stay in denial until it's impossible to be in denial again. It's just one time. It's ok.
Underswap Papyrus - His soul physically cracks when he understands his S/O doesn't recognize him. Honey starts to hyperventilate, both because a cracked soul is extremely painful and because his worst nightmare is coming to life. Honey knows he won't survive your death, and he is ok with the idea. He just hoped... You two would have more time than this. He doesn't want the end of your life to be like this. He doesn't want to sit in this empty room he hates until you pass. The next day, he poisons you and himself and simply goes to sleep next to you, hugging you close.
Underfell Sans - Red is destroyed. Those last days had been exhausting, and this is just the last nail in the coffin. Red tries to take a deep breath, but it doesn't stop the tears from running down his cheeks. He hates himself. He's not supposed to cry. Monsters like him don't cry. But it hurts so much, and it's so unfair, and he's MAD. He's so mad at the entire world. You deserve way better than this. Red forces himself to calm down as you stare, worried, and he just lies on the bed with you. It's ok if you don't remember him. He can do it for both of you. Red is extremely loyal, and he knows he won't be ok once you're gone, but as long as you're here, he will be by your side.
Underfell Papyrus - Edge freezes completely, not believing what's happening. He simply stares at his S/O in shock and pain because he knows they didn't do it on purpose, but he can't help it. It hurts. It hurts really bad. He already saw other monsters with dementia, but... But it was not the same. It was not his S/O. It could distance himself and act like he doesn't care. He can't now. He can't pretend that didn't happen; he just can't. He takes a deep breath, trying to act like that didn't happen, but his voice is shaking. He tells you that it's ok, even though he doesn't believe a word he says. He is panicking. He is scared. He is so so scared.
Horrortale Sans - You two made a promise to each other that if one day one of you didn't recognize the other, you would decide to stop everything together. Oak smiles gently at you as you start to sob after realizing what happened. He tells you it's ok. You two fought as hard as you could. It's just something that you can't win against, and the same is true with him. You talk about this for long minutes, then Oak picks you up and takes you into the woods with him, where you two simply disappear, never to be seen again.
Horrortale Papyrus - Willow immediately minimizes the situation so you don't feel bad. It's ok, he doesn't mind. Oak forgot about him to. And Old Lady. And you now, but all of them are still around so why would it be different? He is concerned; it's true, but he already dealt with this in the past; he can do it again. It's just something you two will have to get used to. He prefers to stay optimistic. Like he keeps repeating to the other skeletons on the farm, your disability is not what defines you. There is always solutions. It will be alright.
Horrorswap Sans - Nugget shuts down. Well, it was too good to be true, uh? He knew it wouldn't last. Him being happy. It seems the universe found yet another way to remind him he is not a good person and doesn't deserve to have a happy life. He knows he's being dramatic, but he's getting angry and frustrated, and he knows it will lead to no good. He prefers to leave for now. He needs alone time to think.
Horrorswap Papyrus - He keeps signing his name, again and again, more and more distressed as it's clear you lost the ability to read sign language as well. Please... Please, don't abandon him. He's not ready, and he doesn't think he can do this again. He already lost too much; he doesn't think he can move on from this. Please... He takes deep breath, sobbing silently. He is not ok. He needs comfort, and you to say it will be ok. He's not feeling good.
Horrorfell Sans - Copper is a patient guy. It's ok, he can simply remind you who he is, as many times as you need it. Maybe it's like with Oak? He had to repeat himself a bunch of times before he got it. Maybe it works the same, and if he keeps repeating himself, you won't forget him anymore. He is in strong denial. He doesn't want to hear what the doctor has to say. He doesn't care. He knows you didn't forget him. He just knows it, ok?
Horrorfell Papyrus - He just looks at his feet in silence, shutting down. He thought he could deal with it, as he's tough and strong. But it's getting difficult. He knew it would happen eventually; the doctors said it would be worse eventually. He was fine back then; why isn't he anymore? He simply takes his S/O's hand and squeezes it. You're there. Even if you don't remember him, you're there. He can't give up now. It's not fair. He'll be there. He's a little down, but he will find a way to make it work anyway.
Horrorswapfell Sans - He can be whoever you want him to be as long as you don't leave him yet. Bear is terrified of losing his S/O. Sure, they are struggling and not remembering him, and it's scary, but you're still alive and it's all that matters for now. He doesn't care you rejecting him because you don't remember who he is; all he wants is to be sure you are still alive. If the cost to pay for this is you completely forgetting about him, he doesn't mind. He won't move from this chair. He's not leaving your side even if you hate him.
Horrorswapfell Papyrus - So this is it, eh? He knew that day would come, but it went faster than he expected. Tiger knows he should feel some sort of feeling, but all he feels is emptiness inside. It's not that he doesn't care, he cares a lot, but... After everything he went through, he is just tired. He's tired of having to fight and stay optimistic when clearly it's been a long time since his optimism left the party. He just smiles forcefully to not freak you out, and he moves on. He's scared, but it's not like the universe has ever been merciful on him. He'll be ok in the end, he guesses.
Horrorfellswap Sans - Merlot doesn't know what to say, very uncomfortable. He didn't know that could happen, and this is kind of scary. He was aware it was bad, he thinks he didn't realize how much until this moment. He tries to keep a cold head and acts like it's not a big thing, but he keeps thinking about it to the point he doesn't sleep at night anymore.
Horrorfellswap Papyrus - He forces a smile, extremely hurt. He tries to tell you it's ok, but all come out of his throat are distressed sobs, as he reaches his final limit. He can't keep doing this. He can't lose you after losing almost everything to this white room he is forced to leave for years. He can't do it anymore. He simply decides right here, right now, that when it's time for you, he doesn't want to stay alone in that place. He's going too. No one needs to know. It will be your secret.
Swapfell Sans - Nox prefers to not acknowledge it. You forgot all sort of things since the beginning of that illness; it's not worth it taking it personally. He softens and reassures you as you start to panic when you realize. It's ok. It was just a slip-up. It happens. That doesn't mean anything. If even him, a natural pessimist, decided for once to stay optimistic, you better do the same.
Swapfell Papyrus - Wow. He is absolutely terrified. Rus was really good, until that moment, to de-dramatize things and act like your illness is not changing you, but now you're forgetting him, and he starts to freak out. He wants to distance himself so bad, to not have to deal with this like he avoided dealing with important things his entire life, but reality is catching up on him fast. He can't ignore the problem anymore. It's something both of you will have to learn to live with eventually, and he's terrified. He has no idea how to help you. This is scary.
Fellswap Gold Sans - He tries to stay rational and at a distance, but it's complicated to do when you realize after each crisis that you forgot a little more each time. Wine tries to be there to support you when you need reassurance, but he's also aware he is losing you, and that it will hurt badly. He's trying to find a way out of this so he suffers less, but it seems like it's not working. He isn't sure what more he can do to help.
Fellswap Gold Papyrus - Coffee is devastated, and he can't hold his tears, even if he's trying really hard. It's not fair. It feels like grieving, but you're still here. You're still here, and he never felt so lonely before. He is scared. He is scared all the time now, and this is just too much. He doesn't know what to do. He doesn't know how he can help. He is scared, and alone, and he needs help so desperately. Please... Anyone... He doesn't want to be alone dealing with this. He needs help.
