The Samurai's Honor - The Heart of the Samurai, #0.5

Younger daughter of the area's most prominent swordsmith, Sen's life is marked with jealousy, curiosity, and love. Jealousy that her older sister, Haru, gets to marry her father's handsome apprentice. Curiosity about her father's important customers. Love from a family that is planning her next step to adulthood. But when a high-ranking samurai visits her father to order a sword, Sen's curiosity gets the best of her.
She and her sister find themselves eyewitnesses to a murder and on the cusp of a plot that seeks the samurai's demise. Will Sen's curiosity lead to her own death?