After the battle of the Fourth Holy Grail War, Kotomine Kirei, who was revived by the grail's tainted mud, emerged victorious. While Gilgamesh was forcibly incarnated into this era with a physical body after it failed to taint the heroic spirit. Preparation for the next Holy Grail War then begins.

However, much to Kirei's struggle, keeping Gilgamesh, a king, out of trouble was a major problem.

For his plans to unfold perfectly, he has to ensure he is entertained all the time; otherwise, he would roll off the chessboard and cause even bigger trouble for him. But being a priest, an executor, and an overseer, and checking on one as difficult as Gilgamesh was too much work even for him.

Fortunately for him, he has someone as reliable as you around.

(Creator did not make this character or the story lore accurate. Advance apologies because this Gilgamesh was made to cater someone else👀)