This story is set in a feudal society. The couples are Feng Yingsha x Hei Xiangling, and Fei Ling x Qi Na. Feng Yingsha is a wealthy young master born with a disability, and Hei Xiangling is his personal maid. Qi Na is a noble young lady whose parents have both died, and Fei Ling is her personal maid. Feng Yingsha and Qi Na are forced into a marriage arranged by their families, but they are married in name only. They sympathize with and care for one another, but have no romantic feelings and have never consummated the marriage. The four of them find comfort in one another because society rejects them.
The main couple is BG, and the secondary couple is GL. If that's not your thing, please don't read. No ship-bashing.
Theme: Making up for the regrets that never came to pass