Barom One

Takeshi Kido and Kentaro Shiratori are a pair of friends who have been together for almost their entire life. One night, a strange being comes out from the lake and starts attacking them. When Takeshi and Kentaro are almost eliminated, a strange being named Kopu calls them and tells them that they are the chosen ones to inherit the power to protect the world from an evil being named Goumon. (myanimelist.net)