Sisters of the Sword: Game Potential

Recently, I read the YA novel Sisters of the Sword by Maya Snow, as part of my ever continuing research on feudal Japan, Japanese folklore, and feudal Japanese themed stories.

The plot, to my mind, has excellent potential for an RPG campaign starter:

Two sisters, daughters of nobility, secretly witness the murder of their father and brothers and the slaughter of the servants. Vengeance is sworn but the sisters know they are not able to extract it because they do not yet have the training or discipline. When they run to find their mother and infant brother, they are nowhere to be found, but a message found later gives them hope.

That's all you need to know to get started I think.

• As in many good samurai stories, vengeance is prime motivator for the overall story.
• From a game point of view, their lack of ability as low level characters combined with this motivation, provides an in-game purpose to gain levels/ability/skills.
• The PCs have learned a variety of combat skills outside what might be usual for their age, from their brothers and father (in-game justification of starting skills)
• The characters can choose how they want to approach their revenge: whether to expose the murderer by gathering evidence or to strike them down in combat (or whatever other way they can imagine)
• Finding their mother and infant brother (rightful heir to their murdered father's position), if they choose to do so, becomes a sub or parallel plot. 
• Finding their mother and infant brother provides an easy way to motivate characters to travel or to take up side-quests  ("A mysterious letter arrives, you recognize the handwriting as your mother's own") 
• The villain knows the daughters, mother and infant son are not dead and has sent his samurai to find them - life on the run becomes a major catalyst for in-game events.
• There are four ready-made encounter-areas, that the PCs know of, to take from the book:

1. the family home
2. the family shrine hidden deep in the forest
3. the nearby village
4. a dojo of a great master who trained their father, the villain, their brothers and the villain's son (in the book, they stumble on this, but it's certainly possible they know of its location. Also since the characters are girls, they have to disguise themselves as boys to get into the school. If the PCs are girls, then protecting their secret and life at the dojo can become adventures in themselves)

• The master (if they meet him) is a potentially useful NPC, well fleshed out in the book, as are several other students (one of which the author seems to hint is of a ninja clan by birth).

As for the book, to my dismay, this is the first book in a series, which I am now going to have to finish reading because I really want to know how it all turns out!