Shin Kaze no Rondo

A pair of men and women who have made a marriage promise. However, when the man's brother died in the war, the fate of the two became an unimaginable tragedy. The cruel goddess of fate also puts a harsh test on her two children... In 1942, Arisawa Maki and Noshiro Koji, the second son of the Noshiro family, signed a marriage promise. However, Koji's older brother, Ichiro, died in the war, and their fate changed drastically. Koji is married to his widowed brother-in-law, Asami, while Maki becomes Daisuke's wife by the strategy of Koji's younger brother, Daisuke. Over time, Maki and Koji, who have children with each other, eventually have an affair. Suspecting his wife's infidelity, Daisuke burns his brother Koji and sets fire to the mansion. A few years later, Maki's daughter, Natsuo, and Koji's son, Hideaki, fell in love as guided by their souls.
(Source: tvdrama-db.com)