What if Manchuria took the role of Japan?
After Nurhaci unified the Jurchen tribes, Nurhaci delivered a manifesto where he wanted to create a united Manchu state that spoke Manchu and inhabited by the Jurchen, aiming for political independence as the Ming Dynasty deteriorated. Nurhaci said in his speech that modern day Manchu nationalists interpreted as "We’re not trying to took over China, we’re never a part of it in the first place." In 1616, he declared himself Khan and founded the Later Jin Khanate, which later declared itself self governing. The Later Jin Khanate went to war with the Ming to establish their core territory (Manchuria). After Nurhaci's death in 1626 during the conflict, his son Hong Taiji made reforms and renamed the Jurchens "Manchu," ultimately establishing the Manchu Khanate. Once Manchuria successfully conquered their core territory, through a ceasefire in 1634, Manchuria agreed to withdrew and stopped expanding beyond the Shanhaiguan Pass in exchange for the Ming to recognize Manchuria as an independent state and both sides agreed to not step foot beyond Shanhaiguan Pass. The Shun Dynasty took over as the next Chinese Dynasty.
Following the war, Hong Taiji established a core bureaucracy in Manchu Khanate. The Khan of the Manchu Khanate would held supreme, absolute authority over all state, legislative, and judicial matters. The Great Council of the Khanate would be responsible for translating the Khan’s decrees into practice, managed state treasury and collected taxes and coordinated the Eight Banners effectively. They’re appointed directly by the Khan under the advice of his advisors. Provinces in Manchuria would be handled by provincial governors who aimed to collect taxes, supervised regional public works like dikes, canals, and waterways, manage local civil services such as school systems, supervise lower-level local such as prefectures, county magistrates officials and more.
During Hong Taiji’s reign, Manchu Khanate focused on reforming the state such as land tax reforms where provinces are required to report comprehensive figures of their labor service and tax registers annually to monitor population changes and curb local officials' arbitrary use and embezzlement of poll tax revenue alongside the creation of the Complete Books of Taxes and Labor Service where it listed the fixed land tax and poll tax that each province, prefecture and county had to pay each year. By making these tax amounts official, ordinary people could see what they owed, taking away the local officials' ability to change tax rates at will.  Hong Taiji also focused on agricultural growth. This helped boosted the economy of Manchuria. Ijishūn Dasan Khan (the Shunzhi Emperor) became Khan under the regency of Dorgon. Ijishūn Dasan Khan under Dorgon continued Hong Taiji’s previous reforms. Meanwhile, the Shun Dynasty collapsed in just a couple of months due to the Yongchang Emperor’s unpopularity, and with no clear heir, China collapsed once again. Taking advantage of the situation, Manchuria launched a military campaign of Joseon in 1646 which ended in a Manchurian’s victory that year on December, resulting in the Joseon becoming a Manchu’s protectorate. The Lu Dynasty took over as the next and final dynasty of China.
Elhe Taifin Khan (the Kangxi Emperor) took over in 1661. With a combination of Jesuits’s influence, the presence of western traders and Elhe Taifin Khan’s genuine interest on western science caused Manchuria to enter a period of modernization. Elhe Taifin Khan focused on boosting literacy amongst Manchus first. He first created the Updated Manchu Dictionary, which sought to expand Manchu language by adding new words through phonetic transliteration, calquing (semantic translation), hybrid coinages, and adopting the original foreign terms. Later in his reign, he initiated the Translation Project which aimed to translated many western works through the updated Manchu language which would be continued by his successors. Following a Manchurian victory through the Siege of Albazin, Manchuria and Russia signed the Treaty of Nerchinsk in 1689, setting borders and ceding Sakhalin to Manchuria. Before his death, he renamed the Manchu Khanate into the Kingdom of Manchuria (Manchuria being a new word created during his effort to modernized the Manchu language.) with him gaining the title of Elhe Taifin King.
The Hūwaliyasun Tob King (Yongzheng Emperor) took over as King. The Hūwaliyasun Tob King focused on lowering corruption within the Grand Council. He created an Anti-Corruption ministry (Office of Inspector General) to investigate and prosecute illicit favoritism without political interference alongside utilized high-paying salaries to the Office that matched the market to avoid financial temptation. To keep the Minister of the OIG in check from corruption, if the minister is suspected of corruption, the Manchu Justice System would step in and to conduct an independent, thorough investigation. The Hūwaliyasun Tob King also work to transition Manchurian’s army towards more modern weaponry, such as western guns and other firepower. The navy was also an important part of his plan, using newly developed weapons and technology. Abkai Wehiyehe King (the Qianlong Emperor) took the throne. Manchuria reached their absolute peak with the treasury overflowing, agricultural output soared and the population boomed. Many local national banks were chartered as private businesses gained permissions from the government to print money that people could used and Manchuria permit licensed private banks to issue redeemable banknotes. Abkai Wehiyehe King, fueled by a desire to establish Manchuria as the Leader of Asia, drafted a plan called the Greater Manchuria Dream. Manchuria launched an invasion on Japan in 1772, catching the Shogunate off guard. Despite fierce resistances from the Samurais, the Manchu’s navy managed to captured several coastal cities in Japan. Eventually, Japan surrendered in 1775. The Treaty of Nagasaki was signed, the Shogunate would be abolished, the Imperial Family would be restored and Japan would became a Manchu’s protectorate. Britain established an Embassy in Manchuria. Initially trusted by the King himself, Heshen was ultimately punished by the King under the advice of the Office of Inspector General. In his later reign, he establish the Great Manchu Army, which would replace the outdated Eight Banners System and to catch up with the West militarily.
Following Abkai Wehiyehe King’s reign, Manchuria continued to modernized. New ministries were created such as the Ministry of Foreign Affairs, the Ministry of Interior/Civil Affairs, the Ministry of Education and the Ministry of Agriculture. Manchuria starts to built modernized arsenals, shipyards, mines, textiles factories, telegraph systems and more alongside modern schools which taught practical subjects such as Western sciences, mathematics, and practical governance. Agricultural reforms were introduced such as the establishment of agricultural schools. Multiple edicts were passed that would establish a commercial code and corporate laws that would recognize, regulate, and protect private merchant enterprises and joint-stock companies alongside approved and assisted in setting up modern chambers of commerce in major cities to support bankers, traders and business owners later on. Meanwhile as the Lu Dynasty collapsed, Manchuria took advantage of the situation and launched an invasion on Taiwan, beginning the First Sino-Manchurian War, beginning in 1894 to ending in 1895 in a Manchu’s victory. Manchuria would turned Taiwan into a protectorate.
In 1914, Manchuria remains neutral in World War 1 due to a lack of grievances for Manchuria to joined the war. Manchuria continued to industrialized. When the Great Depression hits, Manchuria abandoned their silver standard replaced it with a fiat currency alongside active fiscal spendings, recovering relatively quick than most nations. When the Great Depression hits, Manchuria abandoned their silver standard replaced it with a fiat currency alongside active fiscal spendings and Manchuria engaged in aggressive proto-Keynesian fiscal stimulus. The Bank of Manchuria printed money to purchase government bonds, keeping interest rates low and increase money directly into the economy. However, Manchuria under the Gehungge Yoso King (Xuantong Emperor/Puyi) views that these reforms aren’t enough and that it needed resources somewhere due to the collapse of export economy alongside western protectionism and tariffs. This caused the Gehungge Yoso King (the Xuantong Emperor/Puyi) prepared plans to invade China to secure Chinese’s resources. Using the justification of framing its military expansion as a liberating crusade to free Asian nations from Western and European imperialism, Manchuria launched an invasion on China, beginning the Second Sino-Manchurian War. This was more devastating than the historical Second Sino-Japanese War as Japan, Joseon and Taiwan helped sent military manpower and aid to assist Manchuria in their goals. They surprisingly faced fierce resistance from the United Front through guerrilla warfare against the Manchus. Manchuria captured Beijing but China moved their capital to Chongqing, forcing Manchuria to supply lines into vulnerable positions. In 1940, Manchuria, Germany and Italy signed the Tripartite Pact, acknowledging Manchuria as the Hegemon of Asia. When the West sent supplies to China, Manchuria finally experienced pushbacks. Following Germany’s surrender, Manchuria also surrendered after the nuking of Jilin City and Harbin. Under General Douglas MacArthur, the Gehungge Yoso King would be kept as the King of Manchuria but with his powers purely regulated to ceremonial roles through the 1947 Constitution to maintain public order and facilitating a smooth surrender. Additionally, Manchuria had to renounce their control over Japan, Joseon and Taiwan.
Manchuria oversaw the Cold War between the United States and the Soviet Union, Manchuria sided with the American Bloc. Manchuria initially introduced reforms aimed at reduced tenant dependency on landowners such as rents could not exceed 40% of agricultural output, tenants receiving long-term leases and prohibit land owners from evicting tenants arbitrarily. Eventually, Manchuria began purchasing agricultural land from large landowners in exchange for landowners to receive government bonds, shares in industrial development corporations, etc… lands was then distributed to the peasants with capped ownership so that a single household could only own the amount of land they could farm directly with family labor. In 2010, Manchuria, Joseon and Japan signed an economic alliance similar to ASEAN. The three members would drastically reduced tariffs between the three states to create a single market and production base.
Today, Manchuria is certainly not a top player in geopolitics, but remained a respected nation reputation wise. The current King of Manchuria is the Wenghūi King (Jin Yuzhang, ruling since 2015.)