Grassblades opens with one main character, Masahiro, walking on a forest path. He spots a broken branch with a piece of cloth on it by the side of the path, and goes to investigate. Deeper into the woods, he finds a clearing full of recently dead people - clearly travellers attacked by bandits. As he stands in the clearing, surrounded by blood - the travellers gave as good as they got, and there are dead bandits on the ground as well - he is attacked from behind by one surviving bandit.
He spins around and lashes out with his sword, managing to kill the bandit. As he stands over the newly minted dead body, unsure of what to do, a little girl emerges from the underbrush; she's covered in blood and she doesn't speak, but examines his bloody sword, and then latches onto his leg in the fiercest hug imaginable.
... and that's the story of how Masahiro gets saddled with a selectively mute orphan girl who won't stop following him around.
It establishes a.) the relationship between the two main characters, b.) their personalities (Masahiro is a big grump given to bursts of violence, the little girl he names Akane is quiet and kind of withdrawn, but trusts Masahiro with her life), c.) level of violence in the story, and within the first 16 pages of the story, also d.) a big clue to the reason why Masahiro is wandering around the world with his sword.