15 Now-You-Know Facts That Leveled Up Our Gray Matter

Two young women named Eri and Riko joined the army at the outbreak of the war with China (which started when I was still an undergraduate student). One day while on the battlefield, both girls are captured by enemies who were trying to attack them. They take them with them into a cave where they find something mysterious. After escaping from the enemy, the girls return home and decide to go see the old shrine one more time. While walking through the village, they meet up with an old friend. The friend decides to join them and, soon, all three set off to the ancient shrine in the cave.

Eventually, they make their way to the very heart of the shrine, a cave wall with timeless eldritch runes carved into it by unholy means. The language is one which is no longer spoken except by a handful of local scholars -- and, luckily, their friend is one of them. He deciphers the runes and reads them out: it's a list of fifteen facts, starting with ...