  A new underground lab, Yemilab, is being constructed in Handuk iron mine,
Korea. The default design of Yemilab includes a space for a future neutrino
experiment. We propose to build a water-based liquid scintillator (WbLS)
detector of 4$\sim$5 kiloton size at the Yemilab. The WbLS technology combines
the benefits from both water and liquid scintillator (LS) in a single detector
so that low energy physics and rare event searches can have higher
sensitivities due to the larger size detector with increased light yield. No
experiment has ever used a WbLS technology since it still needs some R&D
studies, as currently being performed by THEIA group. If this technology works
successfully with kiloton scale detector at Yemilab then it can be applied to
future T2HKK (Hyper-K 2$^{nd}$ detector in Korea) to improve its physics
potentials especially in the low energy region.
