Little Quick Authors Note:

When a mishap in a reset happens and a character from another version is transported into the current world and timeline, what happens?
Gaster!Sans, bad-skele-boy from EchoTale is confused to see that he had landed in a different, yet familiar world: Undertale! Apparently, in meeting with his 'original' version, they seem to be OK with one-another, UNTIL...
(Thank you, @yourebluenow for the cover!)
Book 2 Is here! it has the same name and cover, but with 'Part 2' in the title!
https://www.wattpad.com/story/70011017-love-me-instead-sans-vs-gaster-sans-x-reader-part