I Found a Magic Book That Can Turn Me into the Protagonist

"The person who owns this book gets to be the protagonist?"

"This weird magic book fused into my body is worth a billion?"

"If I can't pay, I have to work off my debt?"

"Bah! I'm a proud member of the transmigration army. Even if I die out there, or jump from here, I'm never paying this debt in my life!"

"Wait... Why are there guns in this other world? We can talk this out!"