Kuchi ga Saketemo Kimi ni wa

The Kuchisake-onna, Miroku-san is the bride-to-be of high schooler Kōichi Sano to regain her powers?! And for some reason, Kōichi is totally on board with the engagement… The exciting life of the Kuchisake-onna at the mercy of her high schooler fiancé starts now!
(Source: MANGA Plus)
Note: Chapter count includes 8 extra chapters.