[Amended] Treasury share acquisition: results report

What happened

Treasury Share Acquisition: Results Report 6.0

Sejin T S Co., Ltd.

Amendment Report August 28, 2026

1. Disclosure document being amended: Treasury Share Acquisition: Results Report 2. Original filing date of the disclosure document being amended: 2026-08-25 3. Amended items:

Item 2 (Matters concerning the acquisition report) - (b) Acquisition period: Reason for amendment - Correction of the acquisition period to reflect additional acquisition of previously unacquired shares Before: 2026-08-03 to 2026-08-25 After: 2026-08-03 to 2026-08-28

Item 3 (Acquisition details): Reason for amendment - Correction of the actual acquisition details to reflect additional acquisition of previously unacquired shares Before: Acquired quantity 697,719 shares; Total acquisition amount KRW 1,637,823,370 (see the daily acquisition table in Note 1) After: Acquired quantity 700,805 shares; Total acquisition amount KRW 1,645,999,255 (dates based on trade execution dates; price per share is the average price; price per share and total acquisition amount exclude brokerage fees; see the daily acquisition table in Note 2)

Item 4 (Whether the planned acquisition matches the actual acquisition): Reason for amendment - Correction of the actual acquisition details and the reason for the shortfall, to reflect additional acquisition of previously unacquired shares Before: Planned acquisition amount KRW 1,646,000,000; Total acquisition amount KRW 1,637,823,370. The Company completed the acquisition as close as possible to the planned acquisition amount disclosed in the material event report (treasury share acquisition decision) dated 2026-07-31; the difference is less than the price of one share. A difference arose between the planned acquisition quantity (1,000,000 shares) and the actual acquisition quantity (697,719 shares) due to share-price movements during the treasury share acquisition period. After: Planned acquisition amount KRW 1,646,000,000; Total acquisition amount KRW 1,645,999,255. The Company completed the share acquisition as close as possible to the planned acquisition amount disclosed in the material event report; the difference between the planned acquisition amount and the total acquisition amount is less than the price of one share. A difference arose between the planned acquisition quantity (1,000,000 shares) and the actual acquisition quantity (700,805 shares) due to share-price movements during the treasury share acquisition period.

Item 5 (Treasury share holding status after acquisition): Reason for amendment - Correction of the treasury share holding status to reflect the additional acquisition Before: Common shares 1,292,432; Ratio 15.39%; Total value KRW 2,941,813,604. (As of the filing date of this report, total issued common shares are 8,396,593. The above ratio is the ratio to total issued common shares, and the total value is the treasury-share acquisition cost excluding brokerage fees.) After: Common shares 1,295,518; Ratio 15.43%; Total value KRW 2,949,989,489. (The above "ratio" is calculated by dividing by total issued common shares of 8,396,593. The above "total value" does not include brokerage fees.)

Note 1) Daily acquisition details (before amendment) (unit: KRW, shares) 2026-08-03: Order quantity 83,965; Acquired quantity 83,965; Price per share (KRW) 2,136; Total acquisition amount (KRW) 179,317,990; Brokerage Shinhan Investment Corp. (code 00138321) 2026-08-04: Order quantity 83,965; Acquired quantity 53,965; Price per share (KRW) 2,214; Total acquisition amount (KRW) 119,492,190; Brokerage Shinhan Investment Corp. (code 00138321) 2026-08-05: Order quantity 83,965; Acquired quantity 37,706; Price per share (KRW) 2,197; Total acquisition amount (KRW) 82,855,175; Brokerage Shinhan Investment Corp. (code 00138321) 2026-08-06: Order quantity 83,965; Acquired quantity 83,965; Price per share (KRW) 2,304; Total acquisition amount (KRW) 193,450,215; Brokerage Shinhan Investment Corp. (code 00138321) 2026-08-07: Order quantity 83,965; Acquired quantity 74,415; Price per share (KRW) 2,359; Total acquisition amount (KRW) 175,516,265; Brokerage Shinhan Investment Corp. (code 00138321) 2026-08-10: Order quantity 83,965; Acquired quantity 26,465; Price per share (KRW) 2,347; Total acquisition amount (KRW) 62,106,490; Brokerage Shinhan Investment Corp. (code 00138321) 2026-08-11: Order quantity 83,965; Acquired quantity 83,965; Price per share (KRW) 2,381; Total acquisition amount (KRW) 199,922,770; Brokerage Shinhan Investment Corp. (code 00138321) 2026-08-12: Order quantity 83,965; Acquired quantity 10,020; Price per share (KRW) 2,438; Total acquisition amount (KRW) 24,430,400; Brokerage Shinhan Investment Corp. (code 00138321) 2026-08-18: Order quantity 83,965; Acquired quantity 39,749; Price per share (KRW) 2,380; Total acquisition amount (KRW) 94,601,295; Brokerage Shinhan Investment Corp. (code 00138321) 2026-08-19: Order quantity 83,965; Acquired quantity 70,970; Price per share (KRW) 2,379; Total acquisition amount (KRW) 168,850,490; Brokerage Shinhan Investment Corp. (code 00138321) 2026-08-20: Order quantity 83,965; Acquired quantity 7,373; Price per share (KRW) 2,380; Total acquisition amount (KRW) 17,547,740; Brokerage Shinhan Investment Corp. (code 00138321) 2026-08-21: Order quantity 83,965; Acquired quantity 39,295; Price per share (KRW) 2,590; Total acquisition amount (KRW) 101,774,050; Brokerage Shinhan Investment Corp. (code 00138321) 2026-08-24: Order quantity 40,000; Acquired quantity 40,000; Price per share (KRW) 2,525; Total acquisition amount (KRW) 101,000,000; Brokerage Shinhan Investment Corp. (code 00138321) 2026-08-25: Order quantity 45,866; Acquired quantity 45,866; Price per share (KRW) 2,550; Total acquisition amount (KRW) 116,958,300; Brokerage Shinhan Investment Corp. (code 00138321) Total (before amendment): Order quantity 1,093,446; Acquired quantity 697,719; Average price per share (KRW) 2,347; Total acquisition amount (KRW) 1,637,823,370

Note 2) Daily acquisition details (after amendment) (unit: KRW, shares) 2026-08-03: Order quantity 83,965; Acquired quantity 83,965; Price per share (KRW) 2,136; Total acquisition amount (KRW) 179,317,990; Brokerage Shinhan Investment Corp. (code 00138321) 2026-08-04: Order quantity 83,965; Acquired quantity 53,965; Price per share (KRW) 2,214; Total acquisition amount (KRW) 119,492,190; Brokerage Shinhan Investment Corp. (code 00138321) 2026-08-05: Order quantity 83,965; Acquired quantity 37,706; Price per share (KRW) 2,197; Total acquisition amount (KRW) 82,855,175; Brokerage Shinhan Investment Corp. (code 00138321) 2026-08-06: Order quantity 83,965; Acquired quantity 83,965; Price per share (KRW) 2,304; Total acquisition amount (KRW) 193,450,215; Brokerage Shinhan Investment Corp. (code 00138321) 2026-08-07: Order quantity 83,965; Acquired quantity 74,415; Price per share (KRW) 2,359; Total acquisition amount (KRW) 175,516,265; Brokerage Shinhan Investment Corp. (code 00138321) 2026-08-10: Order quantity 83,965; Acquired quantity 26,465; Price per share (KRW) 2,347; Total acquisition amount (KRW) 62,106,490; Brokerage Shinhan Investment Corp. (code 00138321) 2026-08-11: Order quantity 83,965; Acquired quantity 83,965; Price per share (KRW) 2,381; Total acquisition amount (KRW) 199,922,770; Brokerage Shinhan Investment Corp. (code 00138321) 2026-08-12: Order quantity 83,965; Acquired quantity 10,020; Price per share (KRW) 2,438; Total acquisition amount (KRW) 24,430,400; Brokerage Shinhan Investment Corp. (code 00138321) 2026-08-18: Order quantity 83,965; Acquired quantity 39,749; Price per share (KRW) 2,380; Total acquisition amount (KRW) 94,601,295; Brokerage Shinhan Investment Corp. (code 00138321) 2026-08-19: Order quantity 83,965; Acquired quantity 70,970; Price per share (KRW) 2,379; Total acquisition amount (KRW) 168,850,490; Brokerage Shinhan Investment Corp. (code 00138321) 2026-08-20: Order quantity 83,965; Acquired quantity 7,373; Price per share (KRW) 2,380; Total acquisition amount (KRW) 17,547,740; Brokerage Shinhan Investment Corp. (code 00138321) 2026-08-21: Order quantity 83,965; Acquired quantity 39,295; Price per share (KRW) 2,590; Total acquisition amount (KRW) 101,774,050; Brokerage Shinhan Investment Corp. (code 00138321) 2026-08-24: Order quantity 40,000; Acquired quantity 40,000; Price per share (KRW) 2,525; Total acquisition amount (KRW) 101,000,000; Brokerage Shinhan Investment Corp. (code 00138321) 2026-08-25: Order quantity 45,866; Acquired quantity 45,866; Price per share (KRW) 2,550; Total acquisition amount (KRW) 116,958,300; Brokerage Shinhan Investment Corp. (code 00138321) 2026-08-27: Order quantity 3,085; Acquired quantity 3,085; Price per share (KRW) 2,649; Total acquisition amount (KRW) 8,173,275; Brokerage Shinhan Investment Corp. (code 00138321) 2026-08-28: Order quantity 1; Acquired quantity 1; Price per share (KRW) 2,610; Total acquisition amount (KRW) 2,610; Brokerage Shinhan Investment Corp. (code 00138321) Total (after amendment): Order quantity 1,096,532; Acquired quantity 700,805; Average price per share (KRW) 2,349; Total acquisition amount (KRW) 1,645,999,255

[Restated Report]

Treasury Share Acquisition: Results Report To the Governor of the Financial Supervisory Service August 28, 2026

Company name: Sejin T S Co., Ltd. Representative Director: Kim In-sik Head office address: 51-43 Jimun-ro, Wongok-myeon, Anseong-si, Gyeonggi-do (Phone) 031-650-3700 (Website) http://www.sejints.co.kr Preparer: (Title) Director (Name) Park Yong-seon (Phone) 031-650-3700

1. Name and address of the issuer (a) Name: Sejin T S Co., Ltd. (b) Address: 51-43 Jimun-ro, Wongok-myeon, Anseong-si, Gyeonggi-do

2. Matters concerning the acquisition report (a) Material event report filing date: 2026-07-31 (b) Acquisition period: from 2026-08-03 to 2026-08-28 * The above acquisition period is based on trade execution dates.

3. Acquisition details: identical to the restated 16-row daily table in Note 2 above (acquired quantity 700,805 shares; total acquisition amount KRW 1,645,999,255). * The above dates are based on trade execution dates, and the price per share is the average price. * The price per share and total acquisition amount do not include brokerage fees.

4. Whether the planned acquisition matches the actual acquisition Planned acquisition amount (KRW): Common shares 1,646,000,000; Other shares - Not applicable Actual total acquisition amount (KRW): Common shares 1,645,999,255; Other shares - Not applicable Shortfall: No * The Company completed the share acquisition as close as possible to the planned acquisition amount disclosed in the material event report; the difference between the planned acquisition amount and the total acquisition amount is less than the price of one share. * A difference arose between the planned acquisition quantity (1,000,000 shares) and the actual acquisition quantity (700,805 shares) due to share-price movements during the treasury share acquisition period.

5. Treasury share holding status after acquisition [as of 2026-08-28] (unit: KRW, shares, %) Common shares: Holding under Article 165-3 (A) - Quantity 1,295,518; Ratio 15.43%; Total value KRW 2,949,989,489; Holding under a trust agreement per Article 165-3 (B) - Not applicable; Total (A+B) - Quantity 1,295,518; Ratio 15.43%; Amount KRW 2,949,989,489 Total: Quantity 1,295,518; Ratio 15.43%; Amount KRW 2,949,989,489 * The above "ratio" is calculated by dividing by total issued common shares of 8,396,593. * The above "total value" does not include brokerage fees.

6. Changes in the largest shareholder's shareholding before and after the acquisition [as of 2026-08-28] (unit: shares) Name: Kim In-sik; Type of shares: Common shares; Shares held at acquisition report date: 3,921,700; Shares held at acquisition end date: 3,921,700; Reason for change: Not applicable Total: Common shares 3,921,700 to 3,921,700; Reason for change: Not applicable