Intangible assets, net - Schedule of Intangible Assets (Detail) ¥ in Thousands, $ in Thousands	Mar. 31, 2021 USD ($)	Mar. 31, 2021 CNY (¥)	Mar. 31, 2020 CNY (¥)
Finite-Lived Intangible Assets [Line Items]
Finite-Lived Intangible Assets, Gross		¥ 35,694	¥ 35,694
Less: Accumulated amortization		(6,157)	(2,156)
Intangible assets	$ 4,508	29,537	33,538
Trademark [Member]
Finite-Lived Intangible Assets [Line Items]
Finite-Lived Intangible Assets, Gross		447	447
License [Member]
Finite-Lived Intangible Assets [Line Items]
Finite-Lived Intangible Assets, Gross		3,530	3,530
Dealership [Member]
Finite-Lived Intangible Assets [Line Items]
Finite-Lived Intangible Assets, Gross		¥ 31,717	¥ 31,717

Accumulated amount of amortization of assets, excluding financial assets and goodwill, lacking physical substance with a finite life.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 350
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-Section 50
-Paragraph 2
-Subparagraph (a)(1)
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Amount before amortization of assets, excluding financial assets and goodwill, lacking physical substance with a finite life.

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Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 928
-SubTopic 340
-Section 50
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Sum of the carrying amounts of all intangible assets, excluding goodwill, as of the balance sheet date, net of accumulated amortization and impairment charges.

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