As a Reincarnated Aristocrat, I'll Use My Appraisal Skill to Rise in the World 4 (manga)

Now joined by his politically savvy fiancee, Ars continues striving to turn his weak domain's fortunes around with a little help from his talented vassals. However, everything changes overnight when Ars's father, Lord Raven, is struck by a sudden illness and the duke of Missian is assassinated. With Lord Raven out of action and war threatening at Missian's borders, is Ars prepared to take on his father's mantle?

Volume 4 of the As a Reincarnated Aristocrat, I'll Use My Appraisal Skill to Rise in the World manga series by Natsumi Inoue.