Haitoku Shitei Soukan ~Ane no Midara na Yawaniku~

Ryota feels sorry for her older sister, Misa. Since their parents died she brought him up by herself. One day, she says to him that she is going to marry a man of wealthy family. Ryota thinks she will marry that man for Ryota entering university. He realizes that she is more than just a sister for him.