X-ray spectroscopy of hadronic atoms is a powerful method to study strong interaction between hadrons and nuclei. At J-PARC, we have conducted two experiments, J-PARC E07 and E03, for hadronic atoms with a doubly strange hyperon, Ξ − , aiming at the world-first detection of their X-rays. The first measurement is performed as a byproduct of J-PARC E07 experiment with the hybrid emulsion technique. The second one, J-PARC E03, is a dedicated experiment for detection of Ξ − Fe atom X rays. The preliminary results and the present status of E07 and E03 are shown in this article. Future prospects of Ξ − -atomic X-ray spectroscopy are also discussed. A new measurement has been proposed for detecting Ξ − C atom X rays, where a novel Ξ − tracking method will be applied to realize an improved signal to noise ratio.