Kaihatsu-ryoshu (also pronounced as Kaihotsu-ryoshu) were those who owned the lands they developed as their territories in Shoen koryo sei (The System of Public Lands and Private Estates) in Japan. They were also called konpon-ryoshu.
After Konden einen shizai Law (a law allowing farmers who cleared new lands to own them permanently) took effect in 743, a number of land owners based on konden (newly developed rice field) emerged over an extensive area. Originally, Kaihatsu meant to 'carve out and revive' the land, suggesting not only cultivation of undeveloped wilderness, but also resumption of ruined fields. An award given to developers who resumed ruined fields was at first nothing but the right to cultivate the land on a temporary basis, but eventually evolved into permanent rights in the early Heian period, which greatly motivated Tato (wealthy cultivators) and powerful local clans at Gunji (magistrates) level to cultivate fields. Kokuga (provincial government offices), in turn, used incentives such as exemption from kanmotsu (tribute goods paid as taxes or tithes) to constantly recruit land developers inside and outside of their provinces. However, since in many cases resumed ruined lands would end up being confiscated by kokuga, in the mid-Heian period, a load-style development method of widely taking up and carving out undeveloped wilderness outside of cultivated areas became the mainstream.
Developers would start their development by applying for it to kokuga. First, setting up the development base, they paid development expenses to recruit ronin (masterless samurai) and peasants as workforce inside and outside of their provinces. Kenin (retainers), low ranked people, and followers of the developers acted as managers of the workforce. In parallel with acquisition of labor for the development, construction and improvement of ponds, ditches and dikes were also carried out. At developed farmlands, strong ruling rights were officially given to shoryo (territory) fields and their farmers by kokuga. Within Kokugaryo (territories governed by provincial government office), developed fields were categorized as Gun, Go, Ho, and Bechimyo. Kaihatsu-ryoshu were assumed the position of the officers' organization, such as Gunji (a local government for Gun territory), Goji (a local government official for Go territory), Hoji (a local government official for Ho territory), and Bechimyo myoshu (a local government official for Bechimyo territory), and guaranteed the local load rights, which included the rights for shomu (land management) centered on Kanno (encouragement of agriculture) of developed fields, private tax collection of zoyaku (odd-jobs tasks) and buyaku (labor service), and judgment of criminal cases. The situation for development inside shoen was the same, where kaihatsu-ryoshu were appointed as lower ranked officers or kumon (a local shoen official below the gesu in rank), and so on.
Kaihatsu-ryoshu carefully stored the documents that clearly stipulated the basis of their rights (kugen [a type of certification authorizing a certain privilege to a person]), handing them down for generations. However, it was highly possible that authorization to them were revoked upon the change of kokushi (provincial governors), and also, disputes with other kaihatsu-ryoshu often erupted over such elements as the border. Therefore, kaihatsu-ryoshu tried to secure their dominion and management rights by donating their developed fields to major central nobility, temples, and shrines, that were more powerful than kokuga, to eliminate the pressure from kokuga (those shoen were specifically categorized as donated shoen). In many cases, when donating shoen, kaihatsu-ryoshu were appointed as shokan (an officer governing shoen) by the lord of the manor to whom they donated it. However, also being Zaichokanjin (local officials in the Heian and Kamakura periods), kaihatsu-ryoshu would remain inside the kokugaryo if they determined it would be advantageous for them to keep close ties with kokuga.
In around the mid-Heian period, a number of lower-ranking noblemen with samurai status, who were left out of the central political world, went down to the provinces. Kaihatsu-ryoshu tried to establish the lord-and-vassal relationship with those samurai to facilitate dispute resolution over their shoen. As a result, many kaihatsu-ryoshu became samurai. In the Kamakura period, some kaihatsu-ryoshu were even appointed as jito (manager and lord of manor) or gokenin (an immediate vassal of the shogunate in the Kamakura and Muromachi through Edo periods).