Tozama Daimyo (nonhereditary feudal lord) (外様大名)
The term 'tozama' originally indicated a vassal whose relationship with the lord was not tight.
Tozama daimyo were not involved in the household management within their master's house, and responded instead to the master upon notification of military mobilization or the like. Tozama daimyo could irreprehensively secede from vassalage after the fall of the master's house.
Many of tozama daimyo ruled large domains, however, they were basically not stationed in the vicinity of the locations of strategic importance including Kanto region with Edo in the center, Kyoto, Osaka and those along the Tokaido Road. In the early Edo period, the Edo bakufu (Japanese feudal government headed by a shogun) was wary of tozama daimyo, and condemned them for minor deficiencies, which often resulted in sanction called kaieki: sudden dismissal and deprivation of position, privileges and properties.
Tozama daimyo were generally not appointed to key positions among the cabinet officials of the shogunate such as roju, apart from some exceptions including the SO clan of Tsushima Province, who had traditionally played a significant role in diplomatic relations with Korea, and the SANADA and MATSUMAE clans, who were appointed key positions in the late Edo period. The other such exceptional tozama daimyo included the TODO clan, who served as the TOKUGAWA clan's spearhead and was, in the military, ranked as high as the II clan of the Fudai Hitto (Principal fudai daimyo), and Terumasa IKEDA was ranked as high as shinpan (TOKUGAWA's relatives) and was once expected to serve as the Commander-in-Chief in the Sieges of Ozaka.
In addition, there is a theory that the TOKUGAWA shogunate distinguished between pre-Sekigahara tozama daimyo such as IKEDA, KURODA and HOSOKAWA clans who had maintained close relationship with TOKUGAWA clan well before, and post-Sekigahara tozama daimyo such as MORI, SHIMAZU and UESUGI clans who had submitted themselves to the TOKUGAWA clan's rule after the Battle of Sekigahara, so as to treat the two parties differently.
Incidentally, some tozama daimyo, who were the TOKUGAWA clan's blood relatives or persons of high achievement, were treated equivalently to fudai daimyo, and were also conveniently called jun-fudai daimyo (quasi fudai daimyo).
Major Tozama Daimyo
The Maeda clan (Kaga Domain)
The Shimazu clan (Satsuma Domain)
The Mori clan (Choshu Domain)
The Tosa Yamauchi clan (Tosa Domain)
The Todo clan (Tsu Domain)
The Asano clan (Hiroshima Domain)
The Uesigo clan (Yonezawa Domain)
The Satakae clan (Akita Domain)
The Hosokawa clan (Higo Domain)
The Ikeda clan (Okayama Domain, Tottori Domain)
The Nabeshima clan (Saga Domain)
The Kuroda clan (Fukuoka Domain)
The Date clan (Sendai Domain)
Today the word 'tozama' is often used to mean a stranger.