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1. Undertale: Pen and Sword (UTPaS) by KogetaiKid

   Fandoms: Undertale (Video Game), Deltarune (Video Game), Undertale AU - Fandom  

   • Mature
   • Graphic Depictions Of Violence, Major Character Death
   • Gen, Other
   • Work in Progress

   20 Oct 2026

   Tags

   • Graphic Depictions Of Violence
   • Major Character Death
   • Aqua the Flower & Seth the Flower (Deltarune)
   • Human Souls & Toriel (Undertale)
   • Human Souls & Human Souls (Undertale)
   • Patience Human & Perseverance Human (Undertale)
   • Human Souls (Undertale)
   • Perseverance Soul - Character
   • Patience Soul
   • Toriel (Undertale)
   • Gerson Boom
   • Siblings
   • The Ruins (Undertale)
   • Old Home (Undertale)
   • Snowdin (Undertale)
   • Waterfall (Undertale)
   • Future Fic
   • Emotional Hurt/Comfort
   • Emotional/Psychological Abuse
   • Teenagers
   • Bad Ending
   • perseverance human (undertale)
   • patience human (undertale)
   • au takes place in 203X
   • i hope you guys like what i did with old home ;-;
   • we also meet toriel
   • but thats probably obvious
   • why am i treating ao3 tags like tumblr tags
   • third person perspective (mostlys)
   • seth and aqua are siblings
   • seth also has crushes on people
   • main characters are neurodivergent
   • seth is autistic (undiagnosed)
   • aqua is audhd and dyscalculia (diagnosed)
   • there may be some teen romance but not at the beginning of the fic
   • this version of seth and aqua are very headcanon-heavy
   • i still try to keep their personalities on par with their deltarune selves tho
   • parents are verbally and emotionally abusive
   • Seth is AFAB
   • They/Them Pronouns for Seth the Flower (Deltarune)
   • Seth has a deadname

   Summary

   Once upon a time, two races ruled the Earth: humans and monsters. One day war broke out, the humans won, and they sealed away all of monster kind underneath Mt. Ebott with a magic spell.

   One day, a child under the alias Chara D. fell down the mountain. A little while later, the human died, presumably killed by the monsters sealed away. That's what humanity said happened 201X.

   It's been 20 years since the incident.wh No one wants to talk about monster anymore unless have to teach the bare minimum to fulfill the illusion of education. 14-year-old Seth P. always dreamed of learning more about what truly happened all that time ago. What happened between humans and monsters? And what truly happened to Chara D.

   Despite how it would reveal all answers to them, they never think to actually explore Mt. Ebott, until...

   Language:

   English

   Words:

   16,053

   Chapters:

   3/18

   Comments:

   5

   Kudos:

   2

   Hits:

   25