Capturing Lingjiao

A dark, demonic male antagonist forcibly claims the virtuous protagonist's wife. Forced possession + stealing someone's wife + long-laid plans + a gentle, jade-like beloved + a rival who fights for her and eventually comes out on top. (Not 1v1; tragic ending.) She is the wife of a low-ranking fifth-grade official, a golden-scaled fish trapped in the mud, a beautiful, sharp-edged dagger. Everyone praises her cleverness. Only he knows how cruel and cold she can be. Her husband is an insignificant fifth-grade official with an almost laughably naive faith in the world of politics: upright, refined, kind, and a gentleman through and through. He alone has wanted, time and again, to find fault with her husband. He alone has wanted, time and again, to cover his ears, or choke that gentleman, to bring those tales of "marital bliss" to an abrupt end. As for himself, he is her husband's superior, ill-natured, arrogant, and cold, with a soul as dark as a demon's and as rotted as mud. One day, he dreamed that Shen Lingwei called him "Xiao Huaijin," then called him "husband." He opened his eyes and looked at the woman beside him, whose husband had long since died and whose family had fallen apart. Her hands were bound with ropes. She slept deeply, tears still clinging to the corners of her eyes. He suddenly understood that someday in the future, she would certainly kill him. Only Song and Shen have mutual feelings throughout the story. Xiao, Wen, and Shen are all one-sidedly in love with the female lead.