Days with My Stepsister Vol. 3 (light novel)

 It’s Yuuta and Saki’s first summer vacation as stepsiblings, and they’ll be working at the same bookstore! As Saki’s coworker, Yuuta begins to see a side of her he hadn’t noticed before. But after observing her new coworker for a while, Shiori makes a dark observation—if Saki doesn’t ease up and stop pushing herself so hard, sooner or later she’s going to fall apart. In order to help her, Yuuta will have to make a decision. Should he interfere in his stepsister’s life, even if it means breaking their promise?