A Returner's Magic Should Be Special (Novel)

In the Shadow World, daily life is filled with chaos and catastrophe. Commoner magician Desir Herrman uses his prodigal skills to enter the Shadow Labyrinth-- the peak of the Shadow World. But when his party fails to clear the Labyrinth, humanity falls into demise. This should mean death for Desir, yet he finds himself sent back in time to when he was a boy attending the Hebrion Academy. This is his second chance. Can Desir hone his skills as a magician so he can save humanity the second time around?