Murai Nagatsugu served as a bushō from the Sengoku to early Edo periods.  In the Edo era, he was a retainer of the Maeda family of the Kaga domain.

The original surname of the Murai was Taira – the Kanmu-Heishi from the lineage of Emperor Kanmu in the eighth century.

In 1568, Nagatsugu was born as the eldest son of Murai Nagayori, the founder of the Murai family who became a retainer of Maeda Toshiie while residing in Owari Province under the Oda clan.  When Toshiie absconded from the Oda clan after an incident involving the slaying of a favored tea-server of Oda Nobunaga, Nagatsugu followed Toshiie despite Toshiie’s status as a rōnin, or wandering samurai.

A decade later, in 1569, upon the death of Toshiie’s father, Maeda Toshiharu, Murai Toshihisa, in his role as the eldest son, inherited the headship of the Maeda family.  Nobunaga, however, suddenly ordered Toshiie (in lieu of Toshihisa) to lead the Maeda family.  This owed to the fact that Toshihisa lacked a natural heir and was of frail health.  Nagayori then became a retainer of Toshiie.

In 1599, after the death of Toshiie, Nagayori retired.  When Tokugawa Ieyasu commenced a conquest of Kaga, Maeda Toshinaga tendered his mother, Hōshunin, as a hostage.  Hōshunin had been the formal wife of Toshiie and was, at the time, his widow.  Nagayori accompanied her to Edo; later, in 1605, he died in Edo.  That same year, Nagatsugu wed as his formal wife Maeda Chiyo, later known as Shunkōin, who had earlier separated from Hosokawa Tadataka, and welcomed her into the Murai family.  Chiyo was the sixth daughter of Hōshunin.

Trusted by the Maeda, the Murai became one of the Eight Families of the Maeda, serving as one of their chief retainers.  Each of these families received a fief of more than 10,000 koku for their service to the domain.  The Murai were the eighth family added to the group, receiving a fief of 16,500 koku while serving as the chamberlain of Matsune Castle.  The other families included the Honda, the Chō, and the Yokoyama, in addition to the families of Maeda Tajima-no-kami, Okumura Kawachi-no-kami, Okumura Naizen, and Maeda Tosa-no-kami.

Nagatsugu did not have a child with Chiyo, but had an adopted son, Murai Nagamitsu, and three adopted daughters.  After Nagatsugu’s death, he was succeeded by Nagamitsu, later known as Murai Nagaie.  Their ancestral graves are on Mount Noda.