If you're looking for manga similar to Say "I love you." OVA, you might like these titles.
A self-proclaimed unattractive gloomy high schooler, Hiramiya Reiji, everytime he goes to visit his close friend’s house, he gets messed around by his older sister, Sakuya. Drinking his drink as she pleases, barging into the bathroom, and crawling under his blanket in the middle of the night… Thinking that perhaps he has done something to make her dislike him, he asked his close friend whether he has any idea, but he only gets a reply in a incomprehensible way, “you still haven’t noticed it, huh” On a certain day, Reiji loses in a game and has to listen to 3 of Sakuya’s wishes. Reiji goes along with it even though he has doubts, but could he gradually begin to understand Sakuya’s true feelings…? This is the story of super dense youth and a can’t-be-honest older sister until they become a lovey-dovey married couple――
The daily hardships of Hikage Miyakawa, a young girl who lives with her sister Hinata. Due to Hinata's otaku impulsiveness to constantly buy merchandise, the two girls struggle everyday to have something decent to eat.
Hatsumi Narita lives in a typical company housing complex with her seemingly typical family, but the dramatic turn her life is about to take is anything but, well, typical. Her precocious younger sister Akane is way too popular with boys, her childhood friend Azusa, now a hunky male model, might want to ruin her life, her super-mean and very privileged neighbor Ryoki considers her his slave, and her dreamy older brother Shinogu might not be what he seems at all. What is a hapless heroine to do?