Coronary artery bypass graft (CABG) is the standard of care for unprotected left main coronary artery disease (ULMCAD), largely because repeat revascularization is required after implantation of a drug-eluting stent (DES). Recently, double kissing (DK) crush stenting has been reported to be associated with a lower rate of clinical events than have either culotte or provisional stenting for patients with ULMCAD with Medina 1,1,1 or 0, 1, 1 true bifurcation lesions. Furthermore, the DKCRUSH-V study provided the trend that provisional stenting is effective for simple bifurcation lesions (~70% of entire bifurcations). However, several key issues in provisional side branch (SB) stenting remain to be understudied.