Moshimo no Kimi to Boku

Schwartland is a country surrounded by lakes and forests.
It is said that it is a country where wizards lived long ago. Descendants are normal people except for the royal family who keep their blood pure and inherit power.
Main heroine gets an order to make a dress for princess' birthday party. She visits the castle for the first time and meets princes, priests and young knights. She is allowed by the princess to come freely during 30 days before the birthday. Will that dress be ready in time?

[From vndbreview]