In recent years, neoatherosclerosis and very late stent thrombosis in the extended follow-up period after baremetal stent (BMS) implantation have been recognized. We experienced a case of in-stent restenosis (ISR) detected in a BMS implanted 14 years prior. An 86-year-old man who had a history of BMS implantation because of angina pectoris in the proximal left anterior descending coronary artery (LAD) 14 years previously was referred to our hospital because of worsening chest pain on exertion for 1 month. A coronary angiogram revealed severe stenosis in the previously implanted BMS. Seven days later, percutaneous coronary intervention (PCI) for the LAD lesion was performed. Prior to intervention, intravascular ultrasound (IVUS), optical coherence tomography (OCT), and intracoronary angioscopy were performed, which showed diffuse heterogeneous plaque throughout the stent, various types of imaging in plaques including thrombi and fibrous plaque, and yellow plaques with respective imaging devices. We deployed two drug-eluting stents to cover all the plaque using a filter device in order to protect from distal embolism, and verified the good result by final angiography. From observations obtained with intravascular coronary imaging modalities in this case and knowledge that some past studies revealed, this case was considered as an acute coronary syndrome since neoatherosclerosis rupture in the BMS lesion happened in the extended follow-up period. Therefore we emphasize that physicians have to follow patients who have undergone BMS implantation carefully, even if ISR is not detected in the post early phase.