Ryuu no Shippo wo Kamu Hatsukanezumi

After being thrown out into the streets at age 18, orphan Larin takes shelter at Saltator Manor and poses as a distant relative. Soon, she finds herself whisked away to the imperial palace, substituting for her adoptive sister as the emperor's new concubine. But Larin's noble disguise is not enough to hide her street rat past, and the imperial family threatens to have her killed for deceit. With the emperor vowing to protect Larin through marriage, can the pair overcome their doomed fate?

(Source: Tapas)