Koshikawa is a professor of psychology, Waseda University and the president of the Japanese Association of Mindfulness. Her research interest is the effectiveness of Eastern techniques, such as meditation and yoga, on reducing stress and increasing mental health. The focus of her recent research has been to understand how and why mindfulness meditation has effects on reduction of stress responses and how to use mindfulness meditation to empower people who find themselves stressed and exhausted. Koshikawa has practiced transcendental meditation, Zen meditation, and mindfulness meditation since graduate school. Her first encounter with mindfulness meditation was in a workshop in 1993 by Dr. Jon Kabat-Zinn, who created Mindfulness-Based Stress Reduction. She deepened understanding of it during her sabbatical at University of Oxford between 2003–2004, under Dr. Mark Williams, who developed Mindfulness-Based Cognitive Therapy with Zindel Segal and John D. Teasdale.
In addition to teaching students at the university, she also teaches mindfulness meditation in a mental clinic, a community center and elsewhere to help people cope with stress, anxiety, and depression. Her books include Horizons in Buddhist Psychology: Practice, Research & Theory (A Tao Institute Publication, 2009); Mindfulness: Basis and Practice (in Japanese) (Nippon Hyoron sha, 2016); the Japanese translation (Kitaoji Shobo, 2007) of Mindfulness- based Cognitive Therapy for Depression: A new approach to preventing relapse (Guilford, 2002); Japan (translated by Chun-shu company, 2007); Buddhism Meditation Theories (Chun-shu company, 2008); History of Japanese Buddhism (Shunsha Co., 2015), among others.