Since it's close to Valentines day I'm making it based off a Au party kinda like the Au Christmas Party.
Going through her portal to the Valentines day Au party is what Y/n was doing. She was invited by Sci the younger and scientist version of the other Sanses even Geno was invited and same with Reaper and the others they all were doing their own thing when Y/n's portal opened and she stepped out onto the floor hood over head. Sci went up to her smiling "Welcome to the party, Y/n" he said happily before going back to the others. Reaper and the others looked over at Y/n she was reading F/b a emotionless look on her face that's when Sf asked "How can you be friends with an emotionless freak, Sci?" looking over at Sf. Her eyes filled with nothing Geno's Frisk who had been invited as well growled at Sf saying "You have no idea what's she been through!" "Frisk don't it's fine" "But Y/n you're hurting" "I can't afford to care anymore" that's when Frisk started to sing about Y/n "Just an average girl, she always wore a smile" "She was cheerful and happy for a short while" Y/n's eyes widened "F-Frisk why are you singing that?!" "I-I don't want them to know" Frisk looked over at Y/n with tears in their eyes "They deserve to know" "Now she's older things are getting colder" "Life's not what she thought, she wished someone had told her" "She told you she was down, you let it slip by" "So from then on she kept it on the inside" Y/n's emotionless expression turned into a fake smile "She told herself she was alright but she was telling white lies can't you tell?" Sf looked at Y/n with anger and frustration "Look at her dull eyes" by now everyone was looking at Y/n's dull emotionless eyes as she finally broke down falling to her knees she sobbed. Sci ran to her and helped her up hugging her he gently kissed her kissing back she blushed softly before Sci was about to pull away he kissed her neck. He gave her a love letter she read it silently and blushed more before kissing Sci again which he kissed back "Happy Valentines Day sweetheart" "H-Happy Valentines Day"