The 17 June 2018 M-JMA 6.1 (M-W 5.5) Osaka earthquake exhibits a large non-double-couple component (similar to 26%), and its aftershock sequence shows a complicated spatial pattern. To better understand the ruptured faults, we relocate the earthquake sequence using P and S arrival times and waveform cross correlations and calculate the focal mechanisms of all M-JMA >= 2.5 (M-W >= 2.3) earthquakes within three months after the mainshock using P-wave first-motion polarities and SIP amplitude ratios. Relocated aftershocks image several faults, the northeast-striking strike-slip fault, the north-northwest-striking reverse fault, and at least two small northwest-striking features. P-wave first motions of the mainshock indicate nearly a pure thrust mechanism. We deduce that the earthquake sequence started from a north-northwest-striking reverse fault and propagated to a northeast-striking strike-slip fault. The aligned strikeslip aftershocks occurring in the vicinity of the northeast-striking strike-slip fault delineates the growth of several newly formed or reactivated northwest-striking Riedel shears that are conjugated to the northeast-striking strike-slip fault.