Itō Sukenobu served as a bushō during the Sengoku period. He was a retainer of the Itō clan of Hyūga Province.
In 1555, Sukenobu was born as the son of Itō Sukemune.
In the sixth month of 1571, after the demise of Shimazu Takahisa (the fifteenth head of the Shimazu clan of Satsuma Province), the Kimotsuki clan of neighboring Ōsumi Province began to encroach on the territory of the Shimazu. Itō Yoshisuke of Hyūga Province to the north viewed this as an opportunity to garner control of an area in southern Hyūga known as Masakiin. In the fifth month of 1572, he commenced a large offensive in the Iino area governed by the Shimazu clan. This led to an event known as the Battle of Kizakibaru.
In advance of the offensive, Yoshisuke dispatched a secret messenger to Sagara Yoshihi of Hitoyoshi, having him promise to supply reinforcements for the battle. At night on 5/3 of Genki 3 (1572), with Itō Sukeyasu (Kaga-no-kami) serving as the commander-in-chief, a contingent of 3,000 soldiers comprised primarily of young bushi commanded by Sukenobu (Shinjirō), Itō Matajirō, and Itō Sukeharu (Shūri-no-jō) departed Kobayashi Castle located on the front lines with the Shimazu territory. By early dawn, the forces arrived at Iino and Myōkenbaru. At this location, the army separated into two battalions. One remained at Myōkenbaru to hold-down the base of Shimazu Yoshihiro at Iino Castle while the other, led by Sukenobu and Matajirō went from the village of Kamie alongside Iino Castle and through Kizakibaru with the aim of attacking Kakutō Castle where Yoshihiro’s wife and children were holed-up and defended by a garrison of only fifty soldiers.
Sukenobu first set fire to residences surrounding Kakutō Castle, inciting the Shimazu forces. These fires reddened the night sky in the direction of Kakutō and Yoshihiro was awakened by associates who observed the scene. Yoshihiro, however, had already sent Kikuichi, a blind monk from the Sanbutsu Temple in Iino, as a spy into the Itō territory. Having acquiring this information, he remained calm. Yoshihiro had his men set a signal fire to inform Niiro Tadamoto of Ōkuchi Castle and those in Mangata Castle of the danger. He assigned 60 soldiers to Tōya Yoshikata to serve as reinforcements for Kakutō Castle. Next, he had Godai Tomoyoshi lead 40 soldiers to Nomaguchi on Mount Shiratori and Murao Shigeari to lead 50 soldiers to an old culvert at Honjiguchi to set ambushes. Finally, Yoshihiro had Arikawa Sadamasa remained behind to guard the base while Yoshihiro himself led 130 soldiers to deploy and set-up a camp at 二八坂 located between Iino and Kakutō castles.
Thereafter, the battalion led by Sukenobu commenced an assault on Kakutō Castle. Based on information received earlier, the besieging forces approached the Kagikake entrance connected to the rear gate of the castle, but, owing to the darkness of night along with missteps by inexperienced soldiers, the forces attacked the residence of Kabayama Jōkei at the base of the hill leading to Kagikake. Jōkei and his two sons hurled rocks from above and, while feigning that they were accompanied by many troops, attacked Sukenobu’s battalion. Despite their valiant fighting, they were killed. Afterwards, Sukenobu’s forces continued to head toward the rear entrance of the castle, but, owing to a bottleneck on the route, in addition to the Kagikake entrance being on a cliff, the forces could not proceed as planned, and, instead, endured a barrage of large boulders and arrows. At this time, Kawakami Tadatomo charged out of the castle to attack, and with reinforcements from Mangata and Yoshida rushing to the scene in response to smoke signals, along with attacks by the forces of Tōya Yoshikata, Sukenobu’s battalion was forced to retreat. During this clash, Itō Mokuemon and Mera Shigekata (the lord of Kobayashi Castle) were killed (subject to other theories).
Sukenobu’s battalion retreated down to the Ikejima River, resting on the remains of the Torigoe Castle. The large number of troops offered a sense of security and, owing to the humid weather, many swam in the river. After receiving an update on the situation from a scout named Sawada Hassen, Yoshihiro deployed to launch a frontal assault that resulted in the deaths of many of the Itō forces. Meanwhile, Sukenobu lost in a duel against Yoshihiro and died in Misumida. During the duel, Yoshihiro rode a mare with a chestnut coat. When Sukenobu tried to stab Yoshihiro with the tip of his spear, Yoshihiro deflected the strike when his horse raised its front legs in defense. There is another story by which this occurred in a clash against a retainer of the Itō named Yunokisada Masaie, during which Yoshihiro killed Masaie.
Yoshihiro viewed this as a good time for a temporary retreat. Thereafter, in the Itō army, the division led by Sukenobu converged with the main division and began to retreat to Takaharu Castle via Mount Shiratori.
After the battle, Shimazu Yoshihiro had a traditional stone memorial with images of Kshitigarbha (the Bodhisattva who looks over children, travelers and the underworld) built in Misumida where Sukenobu died in the duel, having respect paid to fallen soldiers including allies and enemies alike. Meanwhile, the Itō built burial mounds in Kobayashi where the fallen were honored.