Supermassive black holes (SMBHs) at the center of inactive galaxies can be detected by tidal disruption events (TDEs). As a star approaches an SMBH in a parabolic orbit, its tidal force destroys it, and the disrupted remnant falls back to the SMBH, producing a characteristic flare that lasts for several months. Recent multi-wavelength and multi-particle observations found that the three accretion flare events (AT2019dsg, AT2019fdr, and AT2019aalc) have a temporal and spatial association with sub-PeV scale neutrinos detected by IceCube. Especially,  AT2019dsg is known to be an unusual TDE that shines brightly in IR, optical, and UV with weak radio emission, revealing the observational diversity of TDEs. This multi-message nature strongly motivates us to consider the mechanism of high-energy neutrino emission from TDEs. A few models have been proposed, but the model consistent with all the observed features has not yet been made. In this talk, I will overview what TDEs are and then share the issues on the high-energy neutrino-TDE association.