v3.26.1
SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Value added taxes, Revenue recognition (Details)
12 Months Ended
Dec. 31, 2025
CNY (¥)
Dec. 31, 2025
USD ($)
Dec. 31, 2024
CNY (¥)
Dec. 31, 2023
CNY (¥)
Revenue recognition        
Cost of revenues ¥ 3,464,294,613 $ 495,387,541 ¥ 2,789,533,350 ¥ 2,081,010,633
Free service period 1 year 1 year    
Transaction price allocated to remaining performance obligations ¥ 281,062,668      
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2026-01-01        
Revenue recognition        
Transaction price allocated to remaining performance obligations ¥ 257,746,493      
Period over which remaining performance obligation is expected to be recognized as revenue 12 months      
Shipping costs        
Revenue recognition        
Cost of revenues ¥ 74,501,053   ¥ 70,938,685 ¥ 52,541,201
Minimum        
Revenue recognition        
Return and refund policy term (in days) 7 days 7 days    
Maximum        
Revenue recognition        
Return and refund policy term (in days) 30 days 30 days