Tasogare is a rich province neighbouring Utakata, Introduced during the events of Tales of the Ninja. It's ruled by Lord Uzuki. To secure an alliance with the province, Ichijo proposed marriage to Princess Azami, Lord Uzuki's eldest daughter, as the lord had been looking for a worthy suitor for her.
Lord Uzuki accepts Ichijo's proposal on the condition that he rid Tasogare of the Kenobi, who had served him for years but now became a hazard to his subjects due to their violent temperaments and stupidity. Ichijo sends the Asuka to expel the Kenobi, which they succeed in doing so.
Some time after this, Princess Azami is sent to Utakata for her wedding, but her entourage is ambushed and herself captured by the Mosu, sent to stop the Ichijo-Tasogare alliance by marriage. Thus, Ichijo sends the Asuka once again to rescue the princess, and later to serve as bodyguards. The night before the wedding the Mosu arrive to take Ichijo's life, but thanks to the Asuka's protection they fail and the ceremony goes uninterrupted afterwards.
As Tales of the Ninja is a side-story game, Tasogare's story and existance are considered non-canonical.