Level-5 is famous in Japan for its Inazuma Eleven soccer games, which according to Sega feature an in-game mechanic that infringes on one of its patents.
The alleged offending mechanic allows players to move their characters using the stylus on the touch screen, as reported by Kotaku.
Sega aims to stop the sale of all eight Inazuma Eleven titles, and is also seeking 900 million yen (approx. $10 million) in damages.
Opening statements were on December 7th. Level-5 is planning to fight the charges, stating "we are preparing our rebuttal and do not have any comments to make at this time."