you're just a lad who was from the city and had to take a vacation in the province. Your relatives happen to be there and live in a house inside a huge farm

During your stay, a certain horse caught your attention and he's been very very well behaved with you, as if showing favouritism

Your uncle lets you name him so you named him "valker"

Except... You knew he could turn into human, since you caught him during the night before