Sachi

Sachi is a member of the Moonlit Black Cats, a small guild formed by real-life schoolmates from a computer club, including its leader Keita, who lived near her before the two of them ended up trapped in Sword Art Online together. Timid and constantly afraid of dying in the game, she avoids combat whenever possible and never intends to leave the safety of the Town of Beginnings for long.

When Kirito briefly joins the guild, Sachi is the one who notices his true, far higher level, and the discovery gives her genuine peace of mind for the first time, his presence makes her feel safe in a game where death is permanent. That fragile sense of safety does not last: not long after, Sachi and most of her guildmates are killed in a trap on the 27th Floor labyrinth.

Though her time in the story is brief, Sachi's death becomes a formative loss for Kirito, shaping his guilt and his later reluctance to let others fight and die for his sake.