Prologue-eseo 30-nyeoni Heulleotda

I "transmigrated" into a world I'd never seen before. For thirty years, I believed I was living in a classic fantasy RPG. I became a war hero, retired, and thought I was finally about to see the ending. But... Those thirty years were only the prologue. It turns out the real story is about an academy? (Source: Naver, translated)