I think you already know but you need to play the other two love interest first
Seems like it's not downloadable. Only web-playable
SPOILER!!!! I think the cat-demon-thing made us do it because Zilas was already dead from the beggining and he only had time until he proposed. I think the demon cat just been cruel by make us stab this cinnamonroll of a man I was like wtf too T-T
