The possible connection between high energy neutrinos in the energy region above 100 TeV and ultrahigh energy cosmic rays (UHECRs) at energies above $10^{19}$ eV motivates multi-messenger observation approaches involving neutrinos and the multi-wavelength electro-magnetic (EMG) signals. We have constructed a generic unification scheme to model the neutrino and UHECR common sources. Finding the allowed space of the parameters on the source characteristics allows a case study to evaluate the likelihood of each of the known source classes being such unified sources. The likely source candidates are transient or flaring objects mainly in optical and X-ray bands. We propose the two feasible strategies to identify these sources. One is to introduce a sub-threshold triggering in a wide field of view X-ray observatory for following up neutrino detections, and the other is to search for EMG counterparts associated with detections of multiple neutrino events coming from the same direction within a time scale of $\lesssim 30$ days. Sources with a total neutrino emission energy greater than $\sim 10^{51}$ erg are accessible with the present or near-future high energy neutrino observation facilities collaborating with X-rays and optical telescopes currently in operation. The neutrino-driven multi-messenger observations provide a smoking gun to probe the hadronic emission sources we would not be able to find otherwise.