Linking Worlds: Collision

Link and his two friends (and other people) were transported to another world to save it. They went on with their mission slowly but surely. Along the way his two friends would die. The guilt of the events would lead to his mental downfall. He would recover, but the regret lingered. At the end of the story, he and his companions would face the evil god, Janus. Their battle would not end well, which would lead to the worlds of Ntaj and Earth merging. Link's journey is not over until he defeats him. That's if he ever goes back to find him.

Your classic isekai tale who returned home.