Where Is the Halo of the Protagonist of My Other World?

A young man on earth who just graduated was accidentally summoned to a different world, but something went wrong with the summoning ceremony. The reason for being summoned is unknown, and the hero needs to find it. What happens in the process of searching for answers is closer to the truth, but more simple and confusing. What secret is hidden behind this... This novel and its characters are purely fictitious. Any similarity is purely coincidental and should not be imitated.