Like the river they take their name from, the Yuasa flow around obstacles to reach their destination. They are devious courtiers and opportunists, and were one of the first families to side with the Church against Valentin. When Alessandro declared his rebellion, they immediately sided with him, and were invaluable in defending his claims until the Twilight Crux appeared. They are said to emulate the Gitany nomads, and have a long-standing rivalry with the inflexible Minamet family.

Many of the other Komaran families consider the Yuasa to be devious, but the Yuasa think of themselves as simply practical. Within the family, nothing is accorded as much prestige as the ability to get things done. While the Yuasa hold a large amount of northern Komaru, their lands tend to be rough and unprofitable, forcing the Yuasa to continuously labor to survive. As such, profit and loss are very real forces to the Yuasa, and any skilled courtier within the family is careful to get the best of any deal he proposes. Ironically, this very wisdom drives the merchant classes away from the Yuasa: unlike the other noble families, the Yuasa know how not to be taken advantage of.

Perhaps because of the family's values, Yuasa culture is unique within Komaru. Of all of the houses, the Yuasa are the least likely to adhere to the status quo. Unlike other houses, the Yuasa show no reluctance in removing a noble's title if he can be proven incompetent or even complacent. As a result, competition for noble titles within the family is extremely intense. While the Yuasa nobility tends to be extremely ambitious, it also suffers from the need to spend much of its time defending what it already possesses.

On the other hand, holding a title in the Yuasa comes with a variety of perquisites. All of the Yuasa do their best to make the lives of the title-holders as comfortable as possible, even while struggling to outperform them. The entire Yuasa hierarchy depends upon having the family's titles be worthwhile goals to strive for. As a result, those in power, even those with minor titles, tend to live as richly as the greatest dukes in the other families.

Although the Yuasa are not a young family, many of the other Great Families still look upon them with suspicion. For the most part, the Yuasa do not seem to care; they consider themselves responsible for keeping the other families on their toes. This attitude sits particularly poorly with the Minamet, who consider themselves too busy to play the Yuasa family's games. The conflicts between the scheming Yuasa and the bearish Minamet are legendary. The Church and the Yuasa have strained relations at best, in part because of the Yuasa predilection for harboring Gitany nomads in their fortresses.

The Yuasa tend to follow the Komaran standards when choosing names. While the Yuasa have bibelot and nouveau factions within their ranks, the conflicts between the two groups do not manifest as they do in other families. Nevertheless, most nouveau Yuasa take French-influenced names, while traditionalist Yuasa favor names of Japanese origin. The Yuasa family's colors are gray, violet, and black.