A sequel from Eden*.

Yuki Sakuraba is the cutest little sister in the world. Although she is only in junior high, she is already as pretty as a model, has well-developed breasts, and has a great personality, too. "Let's play a game! I'm going to beat up my brother today!" "I picked out some clothes that I think you might like? "Big brother, let's take a bath together. It's been a while." But at home, she still acts like a child. I'm just enjoying the friendly sibling relationship with my cute little sister. That's what I thought....... until one day, when it was revealed that we're not actually blood-related siblings! It shouldn't be possible for my sister to be my girlfriend,...... but now things are different! (Source: Dengeki Bunko, translated)

Even with those eyes, you can't understand love! Vivi, a young lady from the countryside who came to the royal capital to work in order to maintain the reputation of her baron family, is a seamstress who prioritizes functionality. Alex, the leader of the Holy Knights, happens to meet Vivi and falls in love at first sight! His doting heart never stops, and they end up living together!? There seems to be a deeper reason behind his actions, but to Vivi, who has no experience with love, it's all incomprehensible... The devoted love of the handsome, scheming duke is too much for a young lady like her. (Source: Kadokawa, translated)