Hello, I am trying to find this manga

It is a shoujo (or a josei) about a romance between two step-siblings. I remember how the cover looked like and the major lines of the description. It had a red cover with a boy having an Afro hairstyle drawn in white. The plot-line goes as follows: the guy is over-protective of his step-sister, and wouldn't let other guys approach her (people thought that he had a sister-complex). He is a college guy whereas she is still in high school. We discover later that he is in love with her but wouldn't admit it because in his eyes, she is the only family he got. He gradually fell in love with her, then was forced to move out of his family's place in order to assume the responsibility of what will happen later: i.e. breaking up with his girlfriend and announcing to his parents that he is in love with his step-sister. I know that the story seems cheesy but it isn't. It is a good manga with a nice drawing style and I would love to read it again. I've tried everything I can think of to find it with no luck insofar. I would be really grateful if you could help me. Thank you.