We participated a workshop to discuss science and technical aspects of the Atacama Large-Aperture Submm/mm Telescope (AtLAST), which was held at 17-19 January, 2018, at ESO headquarter (Munich, Germany). Ryohei Kawabe (NAOJ) gave a talk on an overview of the LST, and Kotaro Kohno (U. Tokyo) presented science cases based on a unbiased spectroscopic deep galaxy survey using a ultra-wide-bandwidth imaging spectrograph. A state-of-the-art technology which allows us to have such next generation instrument was also introduced by talks given by Akira Endo (TU. Delft) and Jochem Baselmans (SRON). We discussed a possibility to merge two large submm telescope projects, i.e., LST and AtLAST, to make such an innovative telescope more realistic.