Okay, to start: Sorry.

Itch.io doesn't tell me when someone responds to my posts, so I had no idea this post was made. 

As for how long the demo should be: I can't answer that.

While my statement of "It's too short" is very accurate, it really didn't encapsulate what was wrong. In the demo you meet the two love interests, meet your sister and friend(?)/Neighbor(?) Then something happens....and that's it. 

I have no idea what either the plot or genre is. (It seems magical, but alot of genre's can be magical)

I don't really know who any of the characters are outside small character traits. 

You  need to develop these ideas a little bit more before I can really say anything constructive or otherwise. I will say you should probably have us go into the head of the main character a bit more. I am going to be looking into the world through his eyes after all. It'd be nice to know what kind of 'lens' he is.