Twenty years ago, the greatest shinobi of all time retired. Having defeated the greatest enemy and become the savior of an entire people, he remained with the saved. He moved away from the world, which took a lot from him, and the world began to forget its strongest warrior.

But the trumpet horn of war prevents sleep, and the thought of a lost son poisons the soul every day.

So he adjusts his glasses and throws his cloak over his shoulders. The eternally drunk companion will sigh, but will follow his main character.

Follow the Battle Mathematician. For the last time.

Author's notes: read carefully (book 4 out of 5)