おしかけプリンセス

Warring states era.
Local daimyo Asakawa is killed in an enemy state assault. His real daughter manages to secretly escape with five vassals. But she fails to give birth to a boy, and hopes for house revival remain only hopes. When boy with Asakawa blood finally is born, it's already modern times. The descendants of the largest five vassals are all girls studying at one school. It's finally the time to fix historical injustice!

[From vndbreview]