Last Round Arthurs, Vol. 5 (light novel)

Luna and Rintarou return from their quest for the Holy Grail to find the doomsday clock has begun ticking down. It is said that global destruction will befall humanity when King Arthur is resurrected from the age of legends, and that fated moment is drawing ever closer. The other candidates for the throne balk at the task ahead of them, but Luna steps up to participate in a final battle that will transcend time, all to impress a certain vassal who goes by the name Rintarou Magami.