Ninja Studio, best known for developing the Izuna: Legend of the Unemployed Ninja series, appears to have closed down. Their company website ninjastudio.com vanished in May and still hasn’t come back online. There are still links back to it on the various Izuna pages.
Success was the main publisher that picked up Ninja Studio’s games. After they pulled back from releasing DS and console titles, Ninja Studio worked with D3 Publisher prior to their acquisition by Namco Bandai.