Unidentified creatures "Archon" suddenly appear and bring the human beings to a crisis of extinction. A special corps "Goulart Knights" is formed to counter attack Archon. The knights have supernatural power to generate "Holy Grail" from their spirits and battle against Archon.

In a Holy Grail War, Mages (Masters) and their Heroic Spirits (Servants) fight for the control of the Holy Grail—an omnipotent wish-granting device said to fulfill any desire. Years have passed since the end of the Fifth Holy Grail War in Japan. Now, signs portend the emergence of a new Holy Grail in the western American city of Snowfield. Sure enough, Masters and Servants begin to gather... A missing Servant class... Impossible Servant summonings... A nation shrouded in secrecy... And a city created as a battleground. In the face of such irregularities, the Holy Grail War is twisted and driven into the depth of madness. Let the curtain rise on a masquerade of humans and heroes, made to dance upon the stage of a false Holy Grail.

Mariko is tough yet kind girl who is really into motorcycles. She ends up in a race to settle things between the rich son of bike maker and herself.

Second season of Guan Hai Ce.