Subaru/Hyper Suprime-Cam (HSC) is the wide-field imager on 8.2m Subaru telescope that has the field-of-view of 1.85 deg2. We have conducted a deep transient survey using HSC. The transient survey was conducted with the help of Chilean astronomers who acquired VLT and Gemini times to make the spectroscopic follow-up observations of high-redshift supernova candidates. We obtained three spectroscopically confirmed high-redshift supernovae at the redshifts of 2.40, 1.97, and 1.85. We also found many high-redshift supernova candidates for which we were not able to obtain spectra to confirm their redshifts. Our discovery indicates that the event rate of superluminous supernovae, bright supernovae that can be detected at such high redshifts with HSC, may be higher that the local event rate. The HSC transient survey resumes on this Oct and many more results would come from the survey.