At the North Fort, Happy Days That I Spend With Everyone! is a Manga/Manhwa/Manhua in english language, REINCARNATION series, english chapters have been translated and you can read them here. You are reading chapters on www.mgeko.nl fastest updating comic site. The Summary is

Paw pads wrapped in white fur. Fluffiness around the neck. A bushy tail. A rounded figure that was the very definition of fur ball! ――A certain Japanese girl had been reincarnated into such a fox cub; Milfiria. Milfiria was told to watch the house by her mother, as the mother left for the capital. However, unable to bear with the loneliness and deciding to chase her mother to the capital, Milfiria became lost in a fort protected by strong knights. Source: Novel updates