The Meiji leaders had promised, rather vaguely, in the 1868 Charter Oath that they would convene assemblies to discuss the affairs of the nation. Yet it was not until the 1880s that they seriously considered the proclamation of a constitution. That they did so was due to the combined pressure of a number of factors that took place in the 1870s and 1880s.

The minken movement 1870s -- apart from samurai discontents that expressed itself in the 1877 Satsuma Rebellion, there were other elements of dissatisfaction in Japan. There were misfits who found themselves incapable of surviving in the new order; ignorants who were suspicious of newfangled devices; landowners who had not a say in the running of the country; poor farmers who found taxation heavier; and intellectuals who praised western political institutions, especially representative assemblies. All of them saw the demand for representative institutions, or 'sminken' (people's rights) as a solution to their various ills.
This sublimated form of political opposition was championed by certain ex-government leaders in the 1870s, particularly Itagaki Taisuke of Tosa. He had resigned in 1873 because of the Korean crisis and because of his resentment of the monopoly of office by Satsuma and Choshu. He and other leaders conducted by means of public meetings and through the press an agitation for the establishment of representative institutions. The ideas of John S. Mill and Jean Rousseau were involved to support this demand. As early as 1874, they had petitioned for the creation of an elected legislature.
In short, the minken movement represented both a protest by the ex-leaders of Tosa and Hizen as well as an agitation of a wide segment of the Japanese populace.

1881 -- turning point -- the Meiji leaders clearly recognized that the minken movement was an attack on their monopoly of power. Most of them, including Ito, Yamagata, and Iwakura admitted that the creation of a popular assembly on western lines would be the most effective means of preventing opposition from growing dangerous. Yet they were not prepared to give such an assembly real power.
On the other hand, Okuma Shigenobu, then Minister of Finance, had more radical views. In a memorandum in March 1881, he advocated a parliamentary form of government in the English manner (a cabinet responsible to parliament) and suggested early action: 1881 framing of a constitution, 1883 the first elections. In so doing, he wanted to put himself at the head of the minken movement. Okuma's proposals were rejected by his more conservative colleagues, and he was ousted from office in October 1881.
In the meantime, there was an outcry of public criticism of certain supposed scandals concerning the sale of government undertakings in Hokkaido. The direct outcome was the creation of two political parties to challenge government authority. The first was Jiyuto (Liberal Party) led by Itagaki; the second Kaishinto (Progressive Party) led by Okuma. They championed for a constitution and coerced the government into action.
In an attempt to disarm opposition, the Emperor announced that the decision to grant a constitution had been taken in principle and would be implemented in 1890. This imperial edict certainly represented a concession by the oligarchy to the minken movement.

Constitutional movement 1880s -- in the 1880s, the government took several steps to materialize its promise. In July 1881, Iwakura presented a memorandum that laid down the basic principles of the forthcoming constitution. He suggested a cabinet responsible to the Emperor; a bicameral assembly with an elected lower house; and an electorate based on a property qualification.
Ito then led a mission abroad in March 1882 to study western constitutions. He stayed mainly in Germany and Austria, studying under Alfred Mosse, Lorenz von Stein, and Rudolph Gneist. He passed by Britain and other countries. No doubt, Ito had found what he had expected in the German example. After his return to Japan, he was entrusted with the responsibility of drafting the constitution.
Between 1884 and 1888, a number of institutional changes were made by the government. In 1884, a new peerage was established; in 1885 a cabinet was created to replace the Executive Council; and in 1888 a Privy Council was set up to become the highest advisory body of the state.
In fact, all these measures were important preliminaries to the granting of a constitution. The peerage made possible an appointed upper house of a Diet. The cabinet established in advance the principle that ministers were responsible to the Emperor, not to an elected legislature. The Privy Council under Ito's presidency examined the constitutional draft under strict secrecy. It was also the organ that had the final say on the interpretation or revision of a constitution.
Finally, on February 11, 1889, Emperor Meiji promulgated the first written constitution of Japan in a brief but solemn ceremony. The action symbolized the important fact that the Meiji Constitution was a gracious gift to his subjects and not a concession won from the Throne by popular demand.