Yumi

Try these:
https://www.mangago.zone/read-manga/what_s_with_this_strange_dream/

https://www.mangago.zone/read-manga/they_say_there_s_a_ghost_in_the_club_room/

https://www.mangago.zone/read-manga/that_sexapparition_mgs/

Not exactly possession but similar :
https://www.mangago.zone/read-manga/did_it_work/

https://www.mangago.zone/read-manga/rainbow_city/

Is this it?

Not you citing the novel not know the manhwa ARE YOU KIDDING ME RN GIRL TAKE THIS
https://readhive.org/series/50056/
THE RAINBOSSI NOVEL I REPLIED LATE CAUSE I WAS LITERALLY READING THE SIDE STORIES TO THIS HOW U GON CITE THIS IN FRONT IF ME AND BE LIKE “what is this”
START PRAYING TO OUR LORD AND SAVIOR AND PET OUR BABY DR.SEOK IN THE HEAD
UGHHHHHHH SO GOOOD
READ IT ALL OKAY? MUST READ
MUST READ

*sniff sniff* so rare to have rainbossi mentioned on mmg questions. Read Rainbow City and cry over these two’s cute interactions okie?
Rainbow City is love
Rainbow City is Life
ALL HAIL CHAEPALI
ALL HAIL ROGER NIM

I just realized that I know this and I forgot the tittle and forgot where i am. So i am going to re-read

Yes , thank you!!

MUST READ, MUST REREAD GRRRRRR WOOF WOOF BARK BARK HDSINCEIHDIBFEFIHFFRHI RAINBOSSI SO GOOD (⊙…⊙ ) ヽ(`Д´)ﾉ

(I love rainbossi ╥﹏╥)

i was just scrolling the questions for no reason, but your replies made me check it out. THANK YOU FOR RECOMMENDING THIS MASTERPIECE ε=ε=(ノ≧∇≦)ノ I NOW KNOW WHY YOU’RE SO ENERGETIC ABT THIS LOLOL

AND NOT YOUR BIO ADVERTISING RAINBOW CITY LMFAOOOOO

DMEJDKEJEHEEUEJ EEEEE YOU GETS ITTT AHHH SHEJSJSKEJDDJ IM SO HAPPY ε=ε=(ノ≧∇≦)ノ

Rainbow City is love
Rainbow City is Life ヽ(`Д´)ﾉ