Key Financial Data Of Group
| Concept | 2020-10-01 to 2021-03-31 | 2021-01-01 to 2021-03-31 | As at 2021-03-31 | 2019-10-01 to 2020-09-30 | As at 2020-09-30 | As at 2020-03-31 | 2020-01-01 to 2020-03-31 | 2019-10-01 to 2020-03-31 | 
|---|---|---|---|---|---|---|---|---|
| Key financial data of group | ||||||||
| Business results of group | ||||||||
| Net sales | 
                                                718,820,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                1,979,825,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                980,602,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Ordinary profit (loss) | 
                                                -151,269,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                -583,378,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                -257,136,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Net assets | — | — | 
                                                1,780,336,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                1,709,388,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                1,824,907,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
| Total assets | — | — | 
                                                2,157,501,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                2,073,338,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                3,000,459,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
| Basic earnings (loss) per share | 
                                                -20.51
                                                
                                             | 
                                                0.18
                                                
                                             | — | 
                                                -105.42
                                                
                                             | — | — | 
                                                -10.93
                                                
                                             | 
                                                -39.81
                                                
                                             | 
| Diluted earnings per share |  | — | — |  | — | — | — |  | 
| Equity-to-asset ratio | — | — | 
                                                0.824
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                0.824
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.607
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
| Net cash provided by (used in) operating activities | 
                                                -444,737,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                157,404,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                304,540,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Net cash provided by (used in) investing activities | 
                                                22,927,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                33,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                -386,012,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Net cash provided by (used in) financing activities | 
                                                224,371,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                -500,818,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                -46,715,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Cash and cash equivalents | — | — | 
                                                747,695,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                945,134,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                1,160,325,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — |