Yuusha Densetsu no Uragawa de Ore wa Eiyuu Densetsu o Tsukurimasu: Oudou Goroshi no Eiyuutan~ is a Manga/Manhwa/Manhua in (English/Raw) language, SUGGESTIVE series, english chapters have been translated and you can read them here.
Yukina was a young man who hailed from the same village as the Yuusha who shouldered the fate of the world. Through a certain incident, he got ahold of the talking spear, Gram. It was a weapon that was on par with the legendary sword the Hero wielded. The first volume of an adventure fantasy of the youth with a realistic growth!