v3.26.1
Intangible Assets - Narrative (Details) - JPY (¥)
¥ in Millions
 12 Months Ended
Mar. 31, 2026
Mar. 31, 2025
Mar. 31, 2024
Disclosure of detailed information about intangible assets [line items]      
Impairment losses ¥ 133,402 ¥ 95,602 ¥ 169,405
Reversal of impairment losses ¥ 113,419   ¥ 35,686
Intangible Assets Other Than Goodwill, Post-Tax      
Disclosure of detailed information about intangible assets [line items]      
Discount rate used in current estimate of value in use 7.10% 5.80% 7.20%
ALOFISEL      
Disclosure of detailed information about intangible assets [line items]      
Impairment losses     ¥ 73,979
EXKIVITY      
Disclosure of detailed information about intangible assets [line items]      
Impairment losses     ¥ 28,477
Gamma Delta T-Cell Therapy Platform And Associated Oncology Programs      
Disclosure of detailed information about intangible assets [line items]      
Impairment losses ¥ 58,173    
ALUNBRIG      
Disclosure of detailed information about intangible assets [line items]      
Impairment losses ¥ 31,877    
Impaired product-related intangible assets      
Disclosure of detailed information about intangible assets [line items]      
Impairment losses   ¥ 163,392