She Is a Senior and Also My Sister

Senior sister, suddenly became my stepsister. This is probably the luckiest 'misfortune' in my life. In high school, we were friends, but we missed each other due to misunderstanding; When we reunited in college, she actually moved into my house and became my sister. A year ago, she was the student council president who was completely unapproachable. A year later, she seemed to be far away from me every day. This period of college life has long gone off track.