The Gwisil clan was a collateral branch of the royal family descending from a younger son of the 26th king, Seong of Baekje. Boksin was therefore a distant cousin of Baekje's last recognized king, Uija of Baekje. His father was named Gwisil Jeongin and seems to be the first to take the name "Gwisil". His name is also romanized as "Kwisil Poksin" and in Japan his name is read "Kishitsu Fukushin". As a relative to the royal family he held the highest rank in court as a minister. The earliest mention of him is on August 28, 627 when "Baekje Jeongeuro" is dispatched as an envoy to the court of the Tang dynasty. At this time he held the rank of Dalsol. Emperor Taizong of Tang dictated that Baekje and Goguryeo would stop their attacks on Silla but in February, 628 Baekje underwent a military coup and they attacked Silla, breaking the agreement.
In 660, Baekje was attacked by the allied armies of Silla and Tang dynasty China. The capital, Sabi, was taken, but Boksin resisted near modern-day Yesan. After King Uija's surrender to Tang dynasty China, Boksin and the monkDochim kindled a restoration movement. They sent for the prince Buyeo Pung, who had been living as a hostage in Yamato period Japan, an important Baekje ally. With some Japanese aid, they gathered the remnants of the Baekje army and launched a series of attacks on the Silla-Tang forces.
Death
In 663, Silla and Tang counterattacked, and besieged the restoration movement at a fortress known as Juryu Castle. At this point Boksin appears to have betrayed the restoration movement. He had Dochim killed and sought to slay Prince Pung as well. However, Pung killed him first, and fled to Goguryeo. The restoration movement was destroyed shortly thereafter at the Battle of Baekgang. Excerpt from Nihon Shoki:
"Vanguard shogun Kamitsukeno no Kimi Wakako took Silla’s twin castles in Sabikinue. The Baekje King Pungjang suspected Boksin of treachery, and so made holes in the palms of his hands and bound him with a leather cord. Then he asked the myriad ministers, “Boksin’s crime is this. Shall we behead him or no?” Then Tatsusotsu Deok Jipdeuk said, “This evil betrayer cannot be released.” Then Boksin spat on Jipdeuk and said, “You rotten dog.” The king ordered a strong man to behead Boksin and pickle his neck."
