Ema Terumori served as a bushō during the Sengoku and Azuchi-Momoyama periods.  Terumori  was a member of the Eda clan who were a kokujin, or local family of influence, in Hida Province, serving as the lord of Takahara-Suwa Castle.

Terumori was born either in 1535 or 1548.  His father is considered to be Ema Tokimori, but there are theories denying this as well.  Terumori received one of the characters in his name from Ashikaga Yoshiteru, the thirteenth shōgun of the Muromachi bakufu.

Conflicts among the kunishū of Hida drew-in Uesugi Kenshin of Echigo Province and Takeda Shingen of Kai Province.  These progressed in correlation with the Battle of Kawanakajima in regard to the four districts of Kawanakajima in the northern part of Shinano Province.  In 1564, Terumori joined Mitsuki Tsuguyori and Mitsuki Yoritsuna in support of the Uesugi clan, whereas Ema Tokimori received support from the Takeda clan, providing an advantage over Terumori and the Mitsuki clan.  As a result, Terumori also reverted to service of the Takeda.  Later in 1564, during the an invasion by the Takeda in Etchū Province, Terumori made contributions in attacks against the Shiina clan.  Nakachiyama Castle in the Niikawa District of Etchū was awarded to Terumori.  Thereafter, Shiina Yasutane also surrendered to the Takeda clan.  However, Yasutane lost to Uesugi Kenshin at the Battle of Matsukura Castle in 1571, after which Kawada Nagachika, a senior retainer of the Uesugi, entered Matsukura Castle so that the territory of the Ema clan and the Uesugi clan came into contact.

Following the death of Takeda Shingen in the fourth month of 1573, Terumori informed the Uesugi (Kawada Nagachika) of this news via a retainer named Kawakami Tominobu.  However, he added an apology to the Uesugi in this letter, giving the appearance of being in service to both the Uesugi as well as their rival, the Takeda.

In the sixth month of 1575, Terumori apologized again to the Uesugi, but, in 1576, he was subject to a conquest of Hida by Uesugi Kenshin, and, together with the Mitsuki clan, surrendered.

On 7/16 of 1578, Terumori murdered his predecessor, Ema Tokimori.  This was to have Tokimori’s younger brother, Ema Nobumori, who had been tendered as a hostage to the Takeda family, to become the head of the clan.

In the third month of 1582, after the Takeda clan was extinguished in connection with the Conquest of Kōshū, Terumori submitted to Oda Nobunaga.

In the sixth month of 1582, Oda Nobunaga unexpectedly died in a coup d’état orchestrated by one of his senior retainers, Akechi Mitsuhide, known as the Honnō Temple Incident.  In the tenth month, Terumori fought against Mitsuki Yoritsuna over control of Hida, and was killed in action at the Battle of Yōkamachi.  This also resulted in the fall of Takahara-Suwa Castle.  He was forty-eight years old.

Thirteen remaining retainers of the Ema clan followed after Terumori, killed themselves on the Ōsaka Ridge, and were buried by locals, where memorials stand today.

Ema Tokimasa was his likely successor but his activities are absent from historical records.