The Other Self ~The Hopeless One at Kitayama's House~

Kitayama Kaito is a first-year high school student known around the neighborhood as "the useless one from the Kitayama household," having an excellent younger brother who excels in both academics and athletics. One night, without any warning and without quite understanding what's happening, he switches places with an alternate version of himself in another world. According to the god who orchestrated this, Kaito apparently possesses "the greatest magical talent in human history," and the god declared something along the lines of "change the world as you see fit with that talent." It's something like a heroic tale of that sort.