Hoshi no Samidare

Synopsis

From Seven Seas:

Everything about college student Amamiya Yuuhi is average: grades, looks, and his blasé outlook on life. So what happens when he awakens one day to a talking lizard, who informs him that there is a gigantic hammer in outer space that is poised to split the Earth into pieces and requests his allegiance in the fight against the forces of evil? Pretend it never happened? Unfortunately for Yuuhi, a bit of coercion in the form of a super-powered princess prevents him from returning to his mediocre life as usual. In the adventure of a lifetime, Yuuhi will join forces with the capricious princess and a motley crew of companions to fight back against an evil mage and his horrifying homunculus before the Biscuit Hammer can destroy the planet.

Official English Translation

Synopsis & details from MangaUpdates