Encyclopedia of Monster breeding

John, a former football prodigy, faces despair after a devastating car accident ends his career. Struggling to cope with his shattered dreams, he encounters a mysterious being offering a chance at redemption. Desperate, he accepts, only to awaken in a fantastical world

As a woman.

Amidst the turmoil of his transmigration he notices a Book with the headline "Monster Encyclopedia" Join John on "her" journey on meeting and "fighting" monsters in another world.