Continue from the last Benzine post. The reason that they love milk is because the growth rate of their human form and unicorns form is different.
When they reach 20 their human form would grow into young adult but their unicorn form only aged 2 months. (They mental state is equivalent to young adult though) So they have the random unexplainable urge to drink milk very often.
Once the human form reach age limit, they go full unicorn and live in that form for the rest of their life.











