I've seen severals threads about European nobility, but there's none for Asian one so let's start with Japan.
Japan had rather unique 'nobility' compared to European where there were courtier clans (the nobles) and warrior clans (samurai clans) who later became daimyos (land lords). Most of them are (or claimed to be) the descendants of Fujiwara, Taira, Minamoto, and Tachibana. Those clan was founded during Heian period (794 – 1185 CE) when the Imperial Court grew too large, and the emperor ordered that the descendants of the previous emperor, for too many generations, no longer be princes, but were given the surname and honour.
Initially, the warrior clans were deemed lesser than courtier non-warrior clans (dominated by the Fujiwara clan) in term of social standing and position in the government in which they were never taking part in the political realms until Taira no Kiyomori (1118 – 1181) was able to climb the ranks of government and basically taking control of it from the courtier. After the Taira clan has been beaten by the Minamoto clan in at the Battle of Dan-no-ura, Minamoto no Yoritomo started the beginning of bakufu/shogunate where the warrior clans held the power and (technically) was the one who ‘ruled’ Japan.
With the end of the Tokugawa Shogunate during Meiji Restoration, the new Meiji government seized the land formerly under direct control of the Shogunate and daimyos who loyal to the Tokugawa. It culminated in 1871 with the abolishment of han system, starting with the other daimyos surrendered their domains to the government in exchange of the position as non-hereditary governors of their former domains (which were renamed as prefectures) and the formation of the kazoku peerage system in place of daimyos and noble courtiers with the ranks of:
1. Prince, the equivalent of a Duke (公爵, kōshaku)
2. Marquess (侯爵, kōshaku)
3. Count, the equivalent of an Earl (伯爵, hakushaku)
4. Viscount (子爵, shishaku)
5. Baron (男爵, danshaku)
The initial rank distribution for kazoku houses of kuge descent depended on the highest possible office to which its ancestors had been entitled in the imperial court. Thus, the heirs of the five regent clans (go-sekke) of the Fujiwara dynasty (Konoe, Takatsukasa, Kujō, Ichijō and Nijō) all became princes.
Other head of clans were also appointed the title of prince for taking a prominent role in national affairs or for their close degree of relationship to the Imperial family such as Sajo, Tokudaiji, Saionji, and Iwakura. Same for several former daimyos such as the heads of the Mōri and Shimazu who were both ennobled as princes in 1884 for their role in the Meiji Restoration.
Excluding the Tokugawas, the initial kazoku rank distribution for the former daimyō lords depended on rice revenue: those with 150,000 koku or more became marquesses, those with 50,000 koku or more become counts, and those with holdings rated below 50,000 koku became viscounts.
The head of the Tokugawa clan, Tokugawa Iesato, became a prince, the heads of primary Tokugawa branch houses (shinpan daimyō) became marquesses, the heads of the secondary branches became counts and the heads of more distant branches became viscounts. In 1902, the former shōgun Tokugawa Yoshinobu was created a prince, and the head of the Mito Shinpan house was also raised to the rank of prince in 1929.
The 1946 Constitution of Japan abolished the kazoku and ended the use of all titles of nobility or rank outside the immediate Imperial Family. However, even though they may have lost their past teritories and power, since the end of the war many descendants of the kazoku families continue to occupy prominent roles in Japanese society and industry.
Unlike in European peerage systems, but following traditional Japanese custom, illegitimate sons could succeed to titles and estates. Also, to prevent their lineages from dying out, heads of kazoku houses could (and frequently did) adopt sons from collateral branches of their own houses, whether in the male or female lines of descent, and from other kazoku houses whether related or not. Also unlike European custom, the adopted heir of a peer could succeed to a title ahead of a more senior heir in terms of primogeniture.