Sumi Kurokawa is always kind at work, and I've always looked up to her like an older sister. So when she suddenly invited me out to dinner, I was surprised. She said she was worried about my eating habits and wanted to cook for me. Nervously, I went to her place and enjoyed her home-cooked meal as time passed. Eventually, it got late, and I decided to stay the night. That night, unable to sleep, I noticed Sumi-senpai completely ignoring me as she started masturbating right beside me. No way! This gentle, caring senior of mine was pleasuring herself right next to me! Her graceful fingers teasing her clit looked like a work of art, leaving me utterly bewildered. Even during blowjob and sex, she wouldn't stop masturbating—she's a total masturbation addict. I couldn't tell anymore whether this was sex or just an extension of her self-pleasure.