The Young Mistress's Little Romance in the Duke's Mansion

In the chilly early spring, Gu Xiyan's sister-in-law from her maternal home arrives seeking shelter, bringing along her two young children. Their faces are weary from the journey, expressions filled with panic and desperation, clearly having reached the end of their rope.

However, Gu Xiyan herself had married into a family of higher status than her own. Now, as a young widow living under the roof of her in-laws, she must always tread carefully and dares not make decisions on her own.

She pleaded with the family's matriarch, the elderly lady. The old woman smiled kindly, her words gentle and tactful, but their underlying meaning was crystal clear: there was no chance.

Leaving the old lady's courtyard, Gu Xiyan felt utterly despondent. She couldn't bear to face the desperate, dim look in her sister-in-law's eyes and those of the two children.

Just then, she caught sight of a tall, stern figure—the legitimate son of the Duke's household, Third Master Lu, the current imperial favorite with a brilliant future ahead of him.
Since her marriage into the family, this man had never once looked her directly in the eye, always maintaining a detached, indifferent air.
Yet at this moment, Gu Xiyan tightened her grip on the handkerchief in her hand and thought, perhaps I should give it a try?
　　
……
Later, Lu Chenglian rose from the brocade canopy, tossing out a sentence: “I’ll speak to Mother first tomorrow.”
Upon hearing this, Gu Xiyan, without a care for her disheveled clothing, hurriedly propped herself up: “What?”
Lu Chenglian straightened his lapels in an unhurried manner, his tone flat and unperturbed: “You’ll change your name and identity, start as a concubine, and we’ll figure out what comes next later.”
Huh?
Gu Xiyan was dumbfounded.
Turning back, looking at the confused expression on the woman on the couch, Lu Chenghai suddenly realized something, slowly furrowing his brows. "What do you mean?"
Gu Xiyan stammered, "I, I have to keep watch for Chengyuan..."
Lu Chenglian's expression froze, then finally he understood.
He stared at her for a long while, then sneered coldly, "Gu Xiyan, you're guarding loyalty for Lu Chengyuan, all the way to my bed?"

Important Pre-read Note:

1) Male is chaste; female is not. When these two become entangled, the heroine's husband had already been declared dead by authorities for nearly two years, so from a modern perspective, there is no moral issue.

2) Later, the heroine's deceased husband returns, leading to a clash between the former and current husbands.

3) The heroine is a young widow from a wealthy family who wants to remain faithful to her deceased husband but is weak-willed, young, and easily tempted by desire.

4) The story is set with some feudal elements, and the heroine's mindset is relatively traditional (I'm not entirely sure if this counts, but perhaps it does?).