Otome Kaijuu Caraméliser

From Yen Press:
Suffering from a rare, incurable illness that causes frightening changes to her body, loner Kuroe Akaishi spends her high school days avoiding all her classmates, especially class idol Arata Minami and his groupies. But when Arata starts making her heart skip a beat with irritating regularity, Kuroe discovers that her illness actually has a big make that MONSTERecret: Romance turns her into Love-zilla, literally!

Official Japapense