Don't Toy With Me, Miss Nagatoro, volume 8

The trolling rolls on with Nagatoro! But who exactly is she? For all the time that she's been pestering Senpai, he doesn't really know that much about her. But that changes when he checks up on Nagatoro at home while she's out sick. There, he meets Nagatoro's older sister, who teases Senpai with the chance to learn Nagatoro's deepest secrets...