| N-2 | 6 Months Ended |
| Aug. 31, 2024 $ / shares | |
| Prospectus [Line Items] | |
| Document Period End Date | Aug. 31, 2024 |
| Cover [Abstract] | |
| Entity Central Index Key | 0000859796 |
| Amendment Flag | false |
| Document Type | N-CSRS |
| Entity Registrant Name | JAPAN SMALLER CAPITALIZATION FUND, INC. |
| General Description of Registrant [Abstract] | |
| Share Price | $ 8.03 |
| NAV Per Share | $ 9.97 |
| Latest Premium (Discount) to NAV [Percent] | 19.50% |
