| Mar 31,
2013 | Mar 31,
2014 | Mar 31,
2015 | Mar 31,
2016 | Mar 31,
2017 | Mar 31,
2018 | Dec 31,
2018 | Dec 31,
2019 | Dec 31,
2020 | Dec 31,
2021 | Dec 31,
2022 |
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| Profit (loss) before income taxes | 115 | 1,507 | 1,696 | 1,282 | 1,239 | 1,230 | 729 | 1,667 | 2,082 | 2,511 | 2,948 |
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| Depreciation | 305 | 1,356 | 1,471 | 1,030 | 921 | 1,131 | 936 | 1,096 | 1,226 | 1,029 | 724 |
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| Impairment losses | - | - | 12 | 48 | 19 | 36 | 163 | 54 | - | - | 8 |
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| Amortization of goodwill | 37 | 37 | 37 | 37 | 19 | 43 | 39 | 46 | 60 | 60 | 62 |
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| Share-based payment expenses | - | - | - | - | 22 | 42 | 21 | 170 | 242 | 103 | - |
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| Increase (decrease) in allowance for doubtful accounts | -1 | -3 | -3 | 71 | -21 | -5 | 23 | 6 | 21 | 0 | -0 |
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| Increase (decrease) in provision for bonuses | 4 | 422 | -82 | -81 | 84 | -43 | -205 | 447 | 53 | 38 | 28 |
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| Increase (decrease) in provision for bonuses for directors (and other officers) | - | 13 | 11 | -28 | 27 | -11 | -9 | 28 | 1 | 0 | 13 |
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| Increase (decrease) in provision for retirement benefits for directors (and other officers) | -4 | -28 | 28 | 8 | 9 | 13 | -11 | -9 | 18 | 12 | 23 |
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| Increase (decrease) in retirement benefit liability | - | 2,030 | -25 | -115 | -137 | -224 | -127 | -140 | -119 | -74 | -163 |
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| Increase (decrease) in provision for loss on construction contracts | 45 | 18 | -24 | -17 | -5 | -9 | 0 | 53 | -63 | 5 | 103 |
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| Increase (decrease) in provision for loss on business liquidation | - | - | - | - | - | - | - | - | - | - | 48 |
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| Interest and dividend income | -1 | -11 | -11 | -18 | -17 | -17 | -14 | -19 | -14 | -24 | -30 |
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| Loss on retirement of non-current assets | 15 | 13 | 141 | 21 | 38 | 21 | 6 | 23 | 3 | 11 | 77 |
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| Gain on reversal of share acquisition rights | - | - | - | - | - | - | - | -87 | - | -11 | - |
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| Loss (gain) on step acquisitions | - | - | - | - | - | - | - | - | - | - | -11 |
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| Interest expenses | 2 | 29 | 18 | 13 | 51 | 42 | 25 | 26 | 21 | 12 | 8 |
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| Decrease (increase) in trade receivables | -441 | 322 | -637 | 372 | -516 | -329 | 28 | 127 | -352 | -1,530 | - |
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| Decrease (increase) in trade receivables and contract assets-OpeCF | - | - | - | - | - | - | - | - | - | - | 1,017 |
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| Decrease (increase) in inventories | -180 | 86 | 2 | 22 | -22 | -28 | -42 | -289 | 254 | -85 | 129 |
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| Increase (decrease) in trade payables | 281 | -651 | 506 | -312 | 458 | -543 | -341 | 74 | -189 | 1,075 | -815 |
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| Increase (decrease) in accounts payable - other | -3 | -155 | -80 | -18 | 23 | -36 | 30 | 121 | -100 | -15 | 60 |
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| Decrease (increase) in other current assets | 19 | -32 | 27 | 117 | 35 | 74 | 68 | -83 | 51 | -76 | -91 |
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| Increase (decrease) in other current liabilities | 16 | -20 | 267 | -327 | 25 | 99 | 0 | 75 | 38 | -86 | -116 |
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| Decrease (increase) in other non-current assets | -8 | 31 | 22 | 20 | -11 | -15 | 5 | -14 | 19 | 5 | -61 |
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| Increase (decrease) in other non-current liabilities | - | - | - | - | - | 38 | -12 | -190 | -9 | -6 | -6 |
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| Other, net | -9 | 105 | 29 | -62 | 1 | -1 | -0 | 12 | - | -0 | - |
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| Subtotal | 151 | 2,989 | 3,397 | 2,111 | 2,223 | 1,486 | 1,315 | 3,185 | 3,255 | 2,954 | 3,953 |
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| Interest and dividends received | 1 | 11 | 11 | 18 | 17 | 17 | 14 | 19 | 14 | 24 | 30 |
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| Interest paid | -2 | -25 | -19 | -14 | -52 | -42 | -19 | -28 | -23 | -14 | -8 |
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| Income taxes paid | -34 | -492 | -563 | -783 | -199 | -652 | -396 | -172 | -754 | -642 | -905 |
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| Net cash provided by (used in) operating activities | 117 | 2,483 | 2,826 | 1,332 | 1,990 | 808 | 914 | 3,097 | 2,492 | 2,323 | 3,070 |
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| Purchase of property, plant and equipment | -140 | -491 | -287 | -520 | -277 | -399 | -319 | -699 | -189 | -59 | -53 |
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| Payments for asset retirement obligations | - | -14 | - | -5 | - | - | -10 | -56 | -20 | -0 | -1 |
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| Purchase of intangible assets | -140 | -325 | -284 | -372 | -805 | -1,911 | -699 | -285 | -329 | -333 | -268 |
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| Purchase of investment securities | -10 | - | - | - | -111 | -4 | -0 | -124 | -1 | -1 | -1 |
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| Proceeds from sale of investment securities | - | - | - | - | - | 23 | - | - | - | 1 | - |
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| Proceeds from purchase of shares of subsidiaries resulting in change in scope of consolidation | - | - | - | - | - | - | - | - | - | - | 144 |
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| Payments of guarantee deposits | - | - | - | - | - | - | -22 | -500 | -7 | -20 | -14 |
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| Proceeds from refund of guarantee deposits | - | - | - | - | - | - | 14 | 182 | 14 | 83 | 41 |
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| Payments into time deposits | - | - | - | - | - | -351 | -227 | -123 | - | -170 | -1,264 |
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| Proceeds from withdrawal of time deposits | - | - | - | - | - | 369 | 306 | 117 | 6 | - | 848 |
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| Net cash provided by (used in) investing activities | -333 | -1,044 | -1,496 | -671 | 785 | -2,102 | -957 | -1,459 | -736 | -500 | -568 |
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| Proceeds from short-term borrowings | - | - | - | - | - | 2,007 | 1,918 | 3,529 | 3,881 | 2,765 | 1,119 |
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| Repayments of short-term borrowings | - | - | - | - | -40 | -592 | -1,848 | -4,471 | -3,329 | -3,252 | -1,718 |
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| Proceeds from long-term borrowings | 600 | 3,000 | - | 1,149 | - | - | - | 1,267 | 1,028 | 80 | - |
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| Repayments of long-term borrowings | - | -3,970 | -720 | -720 | -923 | -941 | -257 | -339 | -557 | -720 | -666 |
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| Repayments of lease liabilities | -6 | -25 | -32 | -21 | -39 | -59 | -36 | -47 | -47 | -23 | -4 |
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| Proceeds from exercise of employee share options | 4 | 51 | 20 | 16 | - | - | - | - | - | - | 24 |
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| Purchase of treasury shares | - | - | -0 | - | -0 | -0 | -0 | -1,267 | - | - | -0 |
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| Dividends paid | -63 | -118 | -219 | -177 | -177 | -177 | -176 | -129 | -244 | -244 | -513 |
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| Net cash provided by (used in) financing activities | 958 | -1,563 | -931 | 339 | -1,449 | 238 | -898 | -1,457 | 732 | -1,393 | -1,757 |
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| Effect of exchange rate change on cash and cash equivalents | 45 | 44 | 45 | 3 | -137 | 10 | -37 | -16 | -3 | 164 | 103 |
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| Net increase (decrease) in cash and cash equivalents | 788 | -80 | 444 | 1,003 | 1,188 | -1,046 | -978 | 165 | 2,484 | 594 | 848 |
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