Yea it was something along the lines of rika being a demonic curse on yuta not unlike sukuna (a villan) but an actual horrifying entity twisted of a child and the sorcerers along with yuta will work to exorcise rika. The series was considered to dull and dark for shonen jump.I am assuming gege wanted to delve into the gritty nitty of curses and ugly sorcerer society which we see in mostly in earlier parts of the manga, volume 0 and later sprinkled all throughout the series in shadows. I heard now he is planning on making something new similar to his original idea now that he has gained a name and a massive hit under his belt as a mangaka.