Yes, you can have a harem with all the girls without any downsides, maybe a few jealous lines here and there, but that's it.
Though I'm planning to have harem ending and one true love ending with each main character. But maybe I'll have an option to break up with the girls right before the ending so you don't need to have multiple saves or playthrough as this will be a long story.
I know right, it even surprised me how adorable liz is.