Fate/EXTELLA

The Moon Cell Automaton is a spiritron computer, which exists on the moon and has the power to grant any wish. All across the spiritron-constructed virtual world, SE.RA.PH, Servants and the Masters who control them fight for the right to be the Moon Cell Automaton’s one owner in a ceremonial conflict known as the Holy Grail War.

Now, the Servant Nero Claudius and her Master have won the Holy Grail War and have obtained the universal wishing mechanism, the Holy Grail.

They also obtained the Regalia, a ring that proves their kingship. With it, they rule over their once-enemy Servants and start a new beginning on the moon’s new world.

But a new enemy has appeared before them. And this enemy has something that shouldn’t exist: another Regalia.

[From official English site]

Fate/Extella: The Umbral Star is the newest installment to the Fate series of games/anime. Developed by Marvelous and co-published by Marvelous and XSeed. This is an action hack and slash game with RPG elements.