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What is spacetime? In order to discuss this fundamental question, we held "1-day Workshop on Quantum Gravity" on July 4, 2019. The talk was very varied. First, Yokokura introduced a formulation of black holes as a configuration of quantum fields. Next, Prof. Izumi discussed the relation of S-matrix unitarity and renormalizability in higher-derivative theories. After lunch, Prof. Ho developed a general discussion of the relationship between dynamical horizon and negative energy. Prof. Yoneya began with the origin of Nambu dynamics and introduced an attempt to quantize it with a Hamilton-Jacobi method. Prof. Matsuo discussed M-theory and a mathematical structure behind it. Finally, Prof. Kawai developed a simple model of how the weak scale comes out of the Planck scale. In addition, there was more applications than expected, and the room was a little small. However, the discussion in the physically dense venue was very active as if a concert in a small venue had a stronger feeling of live, and it was a wonderful conference where the enthusiasm of the speakers could be felt directly. And the participants were in a wide range of fields such as elementary particles, relativity and mathematical physics, and over a very wide range of generations, including master's first grader and retired professor. In this way, it was also very meaningful that active discussions were conducted across fields and generations. Now is the time to study quantum gravity with free ideas.