Concentration of risk (Details Narrative) - 6 months ended Jun. 30, 2025	USD ($)	CNY (¥)
Risks and Uncertainties [Abstract]
FDIC limit	$ 69,846	¥ 500,000
Credit risk description	As of June 30, 2025, cash balance of RMB 340,047,601 (USD 47,501,970) was deposited with financial institutions located in China, of which RMB 329,394,812 (USD 46,013,859) was subject to credit risk. The Hong Kong Deposit Protection Board pays compensation up to a limit of HKD 800,000 (approximately USD 101,914) if the bank with which an individual/a company hold its eligible deposit fails. As of June 30, 2025, cash balance of RMB 740,744,294 (USD 103,476,140) was maintained at financial institutions in Hong Kong, of which RMB 734,166,713 (USD 102,557,304) was subject to credit risk. In Singapore, the insurance coverage of each bank is SGD 100,000 (approximately USD 78,478). As of June 30, 2025, cash balance of RMB 679,441,272 (USD 94,912,591) was maintained at financial institutions in Singapore, of which RMB 677,194,110 (USD 94,598,680) was subject to credit risk. In the US, the insurance coverage of each bank is USD 250,000. As of June 30, 2025, cash balance of USD 7,424,103 (RMB 53,146,181) was deposited with a financial institution located in US, of which USD 6,656,593 (RMB 47,651,884) was subject to credit risk. While management believes that these financial institutions are of high credit quality, it also continually monitors their credit worthiness.

Description of credit risk arising from all financial instruments, whether from an individual counterparty or groups of counterparties. Includes disclosures concerning (a) information about the (shared) activity, region or economic characteristic that identifies the concentration, (b) the maximum amount of loss due to credit risk that would be incurred if the counterparties failed completely to perform according to the terms of the contracts, and any security or collateral for the amount due proved to be of no value, (c) the entity's policy of requiring collateral or other security to support financial instruments subject to credit risk, information about the entity's access to that collateral or other security, and the nature and a brief description of the collateral or other security supporting those financial instruments, and (d) the policy of entering into and information about master netting arrangements to mitigate the credit risk of financial instruments, and a brief description of the terms of those arrangements, including the extent to which they would reduce the maximum amount of loss due to credit risk.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Topic 825
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 21
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482907/825-10-50-21

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Name Accounting Standards Codification
-Topic 825
-SubTopic 10
-Section 50
-Paragraph 20
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482907/825-10-50-20

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