In a broad sense it is a kind of Daikan, but from the Muromachi period on the agents who ruled lands under the direct control of the Muromachi Shogunate were called Daikan, distinct from the Shugodai who was the Shugo's deputy.
The Shugo was often involved in the central government in Kamakura or Kyoto, and would leave his fief for long periods. In the case of a Shugo who oversees several provinces, he would have had even fewer opportunities to observe those for which he was responsible. For that purpose the Shugo would appoint an agent from among his vassals to carry out government affairs in his stead. That is the Shugodai. The Shugodai would place sub-shugodai to be his own agents, thus making many layers of land governance organization in the Shugo's fiefs.
In the beginning of the Muromachi period, the Shugo's family or close relatives, or his chief vassal, or an influential samurai from within the Shugo's fief (kokujin) was appointed (in fact, for those families that had multiple Shugo, there were instances in which kokujin from other fiefs were made Shugodai. Sanuki Province Kozai Clan: Tanba Province Shugodai; Noto Province Yusa Clan: Kawachi Province Shugodai; etc.) increasingly often, and as the positions became hereditary, they replaced the Shugo as effective rulers. The Shugodai were elevated by the Muromachi Shogunate to the status just below the Shugo's shirokasabukuro mosen kuraoi and nurigoshi, and were granted a status that allowed them to use the karakasabukuro mosen kuraoi and nurigoshi, a position one level above the kokujin.
On the other hand, with the decline of the shoen and consequent rise of the so, the social position of local lords and the kokujin class rose and strife broke out in the provinces, and the trend grew toward unilateral rule of fiefs; thus with the growth of feudal daimyo, the Shugodai disappeared along with the Shugo daimyo. In fact, there were examples all over of Shugodai becoming feudal daimyo, such as the Nagao clan of Echigo Province, the Asakura clan of Echizen Province, the Oda clan of Owari Province, the Miyoshi clan of Awa Province, the Uragami clan of Bizen Province, and the Amago clan of Izumo Province.
Shugodai Who Became Feudal Lords
The prime example of that is the Asakura clan. The Asakura clan was in fact a powerful branch of the Ashikaga Shogun's family, and as kokujin were hikan (low level bureaucrats) for the Shiba clan, who for generations held the top position among the sankanrei (three deputies). They joined the western army in the Onin War, protecting General Yoshikado SHIBA, the heir of the Shiba clan, from the Shibukawa clan, but at the suggestion of Katsumoto HOSOKAWA, who held the title of Kanrei (deputy to the shogun) and was leader of the eastern army, they were appointed successors to the Echizen Shugo as a reward for going over to the eastern army, thus becoming Shugo. However, because of the Shiba clan's appeals and the Shogunate's sympathy toward them, after a while it became difficult for the Asakura clan to maintain the position of Shugo, and the descendants of Yoshitsugu ASHIKAGA, who was the second son of the third Shogun Yoshimitsu ASHIKAGA and toppled in a rebellion against his brother of Yoshimochi ASHIKAGA, noticed that they were holding out in under the name of Kuratani Gosho in Echizen Province, made the son of Yoshikado SHIBA to succeed to Kuratani Gosho, gave him the name Yoshitoshi ASHIKAGA, set him up as a puppet Shugo in Echizen and secured effective rule of all of Echizen.
The Shugodai of Izumo Province, the Amago clan, were related to that province's Shugo, the Kyogoku clan, and were appointed Shugodai as their chief vassals. However, in the battles after the Onin War, they gave distinguished service and within the Kyogoku family cultivated their power and overcame the main family to become feudal daimyo, eventually achieving the status of Shugo. In fact, the Kyogoku clan, related to the Sasaki clan (Rokkaku clan), were appointed successors to the Izumo Shugo, but Tsunehisa AMAGO disobeyed Masatsune KYOGOKU and pursued the lord, and by gaining control of Izumo expanded it into a great country spanning 11 provinces. Because Tsunehisa's son Masahisa AMAGO fell in battle, Masahisa's eldest son became Tsunehisa's successor. Tsunehisa gave his grandson one of the Japanese characters from Shogun Yoshiharu ASHIKAGA's given name ("haru"), naming him Haruhisa AMAGO, and achieved a promotion to become the Shugo (Governor) of Izumo.
Furthermore, at first the Echigo Shugodai, the Nagao clan, did not go for the Shugo position, but ran the lord out, and Tamekage NAGAO, who even killed the Kanto Kanrei, contributed to the court and the Shogunate and received the status of shirokasabukuro mosen kuraoi, which was the status of a Shugo, and was given part of the name of the 12th Seii taishogun Yoshiharu ASHIKAGA to be called Harukage NAGAO, thereby gaining status on the level of a Shugo while a Shugodai. In the end, Tamekage's second son Kenshin (the latter Kenshin UESUGI) took over from the sickly Harukage, expanded their political power, fought many bloody battles with the Takeda clan, conquerors of Koshin; finally at the request of Norimasa UESUGI of the Uesugi clan who were under attack and losing ground to the Hojo clan, he succeeded to leadership of the Uesugi clan and Kanto Kanrei, thereby achieving a position higher than any regular Shugo.
In this way, the position of the Shugodai, which was nothing more than an agent of a Shugo in the Muromachi period, at the opening of the Warring States period overtook that of the lords and became one of replacing them.
On the other hand, even though they succeeded for a while in becoming feudal daimyo, there are many examples of them later being overthrown by their vassals. The Miyoshi clan are the prime example of this. The Miyoshi clan, as important vassals of the Hosokawa clan, were Shugodai in Awa. In fact, the Miyoshi clan were relatives of a notable branch of the Kai Genji clan, the Ogasawara clan, which had served as Awa Shugo in the Kamakura period, but in the Muromachi period they were Shugodai who protected the Awa Shugo, the Hosokawa clan. Their employer was a branch of the Hosokawa clan that served as Awa Shugo, but when Sumimoto HOSOKAWA was adopted by the head of the clan, Masamoto HOSOKAWA, they went into lands under imperial rule, to support the longstanding desire of Sumimoto HOSOKAWA to be head of the Hosokawa family and the Shogunate's Kanrei, and supported that by establishing battle positions.
Based on a false charge by uncle Masanaga MIYOSHI, Nagayoshi MIYOSHI, whose father was killed by Harumoto HOSOKAWA, requested of his lord Harumoto the position of Daikan over 17 Shogunal properties and the suppression of Masanaga, but when this was sidelined he set up Ujitsuna HOSOKAWA as lord, and turned his back on Harumoto. When Harumoto ran away with father-son Shoguns Yoshiharu ASHIKAGA and Yoshiteru ASHIKAGA to the protection of the Rokkaku clan, the Miyoshi clan made Ujitsuna into a puppet and held the capital with a nominal Kanrei, eventually reconciling with the Shogunate and expanding their rule over all Imperial lands with the Shogunate and Kanrei as puppets. In the end, the Miyoshi clan itself gained the status of Shugo, was picked for Shobanshu, which is chosen from among the powerful or famous Shugo, and ended up with the rank of Jushii-ge and permission to use the nurigoshi which was a symbol of the Shugo's status. However, even though the Miyoshi clan's power grew, their household affairs were eventually taken over by their chief vassal, Hisahide MATSUNAGA. While Nagayoshi MIYOSHI was alive the Matsunaga clan obediently followed their lord, but made accusations against him, pursued political rivals one after another, and after Nagayoshi's death achieved a partially independent position themselves as feudal daimyo centered around Yamato Province, were granted rank and status equal to that of their employer by the court and Shogunate, and eventually surpassed them.
The Shugodai of Owari Province, Nobutomo ODA, also propped up his lord Yoshimune SHIBA as a puppet Shugo, and used him as a justification for his own predominance and expansion of power within Owari Province. However, even though the lord eventually opposed him and sought to drive him to suicide, he was blamed by his relative and vassal Nobunaga ODA for the murder of his lord and overthrown.
The Uragami clan that held power in Bizen Province were also another family that became feudal daimyo for a while, before they were overthrown by their subordinates in the Ukita clan. The Uragami clan had their base in Harima Province, and as chief vassals of the Akamatsu clan who were the Shugo over Harima and Bizen Provinces, had served as the Shugodai of Bizen for generations. However, at the time of Munekage URAGAMI they rebelled against their masters and eventually secured an independent position as feudal daimyo in Bizen Province. However, eventually the Ukita clan, who were powerful kokujin in the same family, deposed the Uragami clan and usurped the rule of that fief.