[Digital Today reporter Sangyeop Oh (오상엽)] The KOSPI soared more than 600 points in a single day to break above the 7,800 mark. Institutions turned net buyers of more than 2 trillion won, and news of a deal in wage and collective bargaining negotiations at Samsung Electronics added to the move, triggering a wave of buying across semiconductors and heavyweight shares.

The KOSPI on May 21 ended up 606.72 points, or 8.42 percent, at 7,815.67. The index, which had slipped to the 7,200 level the previous day, rebounded sharply in a day and completely flipped market sentiment.

Institutions led the rally with net buying of 2.8845 trillion won. Individuals and foreigners posted net selling of 2.6404 trillion won and 241.0 billion won, respectively.

Foreigners extended a net selling streak to 11 consecutive sessions, but selling pressure eased from the previous day.

Most of the top market-cap stocks surged. Samsung Electronics rose 8.51 percent to 299,500 won, closing just shy of the 300,000 won level.

The market views news of a deal in wage and collective bargaining negotiations at Samsung Electronics as having helped improve investor sentiment.

SK Hynix closed up 11.17 percent at 1.94 million won, and SK Square jumped 14.58 percent.

Hyundai Motor climbed 12.50 percent, while Samsung Electro-Mechanics gained 13.48 percent and Samsung Life rose 13.78 percent. HD Hyundai Heavy Industries added 5.66 percent, Doosan Enerbility rose 7.01 percent and LG Energy Solution gained 4.29 percent.

The KOSDAQ also rallied. It ended up 49.90 points, or 4.73 percent, at 1,105.97.

Buy sidecars were triggered in both the KOSPI and the KOSDAQ on the day. Program buying quotes were temporarily halted early in the session as index futures surged.

It was the first time buy sidecars were triggered simultaneously in both markets since April 8.

In the Seoul foreign exchange market, the won fell to 1,505.50 per dollar, down 7.00 won, or 0.47 percent, from the previous session.

The market analysis is that expectations for earnings led by semiconductors and artificial intelligence were strongly reflected again, helping investor sentiment recover quickly a day after a sharp drop.

The assessment is that the KOSPI's upward momentum strengthened further as institutional funds flowed heavily into large-cap shares.