A teaser site with 80-hour countdown has launched at http://project-cosmos.jp. What fans quickly noticed was that, in addition to a registration from Marvelous, its source had a reference to the Fate/Extra game series.
Marvelous published Image Epoch and Type-Moon's Fate/Extra RPG for the PSP in 2010, then Heaven's Feel-esque follow-up Extra CCC in 2014. The Fate/stay night alternate universe/spin-off might best be known for its introduction of its red-clad playable Saber.
Akiyuki Shinbo helmed a SHAFT-animated opening for the games