Inkou Haden Amatsu ~Hakudaku no Juin~

A peaceful island, Amatsu... but the peaceful life on Amatsu is about to finish due to the invasion of Brevis. Seito fights against them but he is defeated, captured and cursed.... He somehow runs away from them and comes to Nakuru. There is a tradition in Nakuru taking over generations that if one gets "St. Gun", they will be able to get rid of any curse. Seito makes up his mind to go for it and sets off on a journey with two Mikos....