Days with My Stepsister Novel Volume 4 was written by Ghost Mikawa with illustrations by Hiten.

When Saki called Yuuta “Big Brother,” it looked to everyone else like their relationship had taken a big step forward. In reality, it was more like a line drawn in the sand. As their hidden feelings make time spent together increasingly awkward, the two of them explore new relationships and weigh their priorities. Are some things worth holding onto despite the sacrifice, or is it time to let go and move on?