3rd person pov

Y/n's f/c soul floated into the air, making b/n burst into tears quietly; mumbling "no" over and over again. Everyone was upset, accept for chase; who was just glad that his ex was gone. Sans' soul suddenly pulsed out of his chest, and y/n's soul rushed toward it. The collision created a bright light that knocked chase, and only chase, against a nearby wall. The next thing everyone knew, sans had a slightly new appearance. Sans' pinpricks were the same, accept sometimes they changed between white, and e/c. Sans' hoodie also changed; the usual white fluff that covered the hood now had f/c tips. Sans blinked and his pinpricks turned e/c. Y/n then said through sans' body "hi guys.... heh, told ya I wouldn't leave". B/n snapped and said/ yelled "ok but now what? How are you supposed to work or go to the roller rink or keep me company when your soul is half absorbed by sans; a skeleton that doesn't even live in our apartment?", b/n drew in a shaky breath as y/n looked down in shame. Sans could see how upset b/n was from y/n's line of vision since she's in control at the moment. Y/n was ashamed of her own actions and put sans back in control again, however y/n's luminescent f/c tears still found a way to leak out of sans' eye sockets. Alphys stammered an explanation to b/n "h-human souls can o-only absorb o-or be a-absorbed by a m-monster soul, a-and vice v-versa. I'm s-sorry b/n", "n-no" y/n said, only controlling sans' voice. "I'm the one who should be sorry. I acted without thinking, again; and now I pay the consequence. I'm paying all of my consequences.... and I deserve each and every one of them". Sans put himself in control and said "don't say that y/n". Y/n took control again and said "to late, already said it", before handing over the controls to sans. Alphys interjected without stuttering, saying "y/n, toriel and I will do our best to keep your body in living condition, once your body is inhabitable again your soul can go back into your body". Y/n took over sans again and said "thanks alphys, this means a lot; and b/n, I'm sorry but I don't wanna mess with sans' life more than I already have. I'll only take control when you all want me to, but as of right now, I wanna let sans keep his body". Y/n let sans take control, sans' pinpricks changed back to white. There was then an awkward silence, alphys and toriel then left with y/n's lifeless corpse, heading to the lab. Papyrus offered to stay with b/n, since he didn't want b/n to be alone. B/n accepted papyrus' offer, and sans was now living alone with y/n in his head. Literally.

(Time skip 2 weeks)

Sans' pov

Y/n and I were both watching a show called Steven universe that she got me into, when my phone began to ring. I paused the show and saw that alphys was calling me. I picked up the phone and said "heya alph, what's up", alphys said "y/n's body is in stable condition, we need you to teleport here and get y/n back in her body. Now!". Alphys must've been serious, cause she wasn't stuttering one bit. I hung up and teleported to the lab. alphys and toriel were there, along with y/n's body. Y/n made her soul detach from sans' soul, and flew back to her body. There were two bright lights coming from y/n and I, and I felt myself return back to normal. I noticed that my hp went up though. My hp went up from 1 hp to 5 hp. I looked at my soul, and saw a small f/c shard fixing the cracks that used to be there.

Y/n's pov

As the bright light engulfed me, I could feel my body becoming my own again, though I felt a little weird. The light eventually faded, and sans looked like he was back to normal, which I was glad for. However, while I was basically in sans' head, I found out that he has a crush on me. I blushed at the thought, but quickly changed the subject with b/n. I quietly said "b/n", and then bolted for the door. My legs were weak from not moving them for two weeks, but I didn't care. I began to think of my apartment with b/n, and how I wanted to hug him. Out of nowhere, everything went black and then I was in the apartment. I was confused for a second, but once I saw b/n I ran up to him and tackle hugged him. B/n was surprised nonetheless, but when he saw it was me, he quickly returned the hug. I could feel b/n get emotional on me, so I said "don't cry b/n". B/n took a deep breath and held my shoulders, pulling out of the hug. B/n then said "don't you ever scare me like that again", I smiled a bit and said "hey it's not like I planned on getting killed, jeez". B/n then gave me a sly grin and asked "so, are you and sans a thing yet?", my face heated up in an instant and I just hid my face in my hands. B/n teased "you're blushing~", I just yelled back "I know and I hate it". B/n laughed and said "man I missed you", just then sans appeared near the door looking panicked and exhausted. I suddenly became concerned and asked "sans what's wrong?". Sans caught his breath and said "alphys wasn't done talking to you. She wanted to tell you that we might have a bit of each others soul now. I think you can use a small about of skeleton magic from my soul, and I gained a bit of determination from your soul". I said "sorry about that, I was just excited to see b/n again".