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1. Side Character by denzelfire

   Fandoms: Undertale (Video Game)  

   • Mature
   • No Archive Warnings Apply
   • Multi
   • Work in Progress

   18 Feb 2026

   Tags

   • No Archive Warnings Apply
   • Sans/Original Character
   • Papyrus/Original Character
   • Sans/Reader
   • Papyrus/Reader
   • Sans (Undertale)
   • Papyrus (Undertale)
   • Reader
   • Original Characters
   • Frisk (Undertale)
   • Angst
   • Jealousy
   • Soulmates
   • Healthy Sibling Relationships
   • One-Sided Attraction
   • Twins
   • Reader Is Not Frisk (Undertale)
   • Reader Is Not Chara (Undertale)
   • Alternate Universe - Underswap (Undertale)
   • Alternate Universe - Underfell (Undertale)
   • Alternate Universe - Swapfell (Undertale)
   • Will add tags along the way
   • Other AUs later
   • Oblivious Reader
   • oblivious twin
   • Reader is not named but the twin is
   • self doubt
   • Alternate Universe - Gaster Bros
   • reader presents as female but they/them pronouns is used
   • their looks is also up in the air
   • readers second job is exotic dancing/bartending
   • Haphephobia
   • Slight Panic Attacks
   • Alternate Universe - Horrortale (Undertale)

   Summary

   You've been friends with the skeletons since they moved in a few months ago. You consider them all to be your friends, best friends even. You decided to invite your twin over to meet them after they moved in with you.

   For some reason all the skeletons seem to have fallen for your twin and they ask you for advice. You're fine with it since your twin likes them too!

   But then why does it hurt so much?

   (rating has been bumped due to one of the jobs the reader has)

   Language:

   English

   Words:

   55,713

   Chapters:

   22/?

   Comments:

   589

   Kudos:

   1,521

   Bookmarks:

   297

   Hits:

   34,812