I play tennis on weekends usually in a park and I wander around in there to see if there is any beetle on a tree in summer. This beetle is a typical Japanese one and seen not only across this nation, but also in China, Taiwan, and the two Koreas. But I rarely find one usually, and this was the first beetle I saw this year.
Japanese coleopterans are usually smaller than foreign ones such as Hercules beetle in Latin America, and this one was just about 6cm long.
You can find this beetle all day in summer, but as a hornet sometimes happens to be on the same tree during the day, it would be better if you go catch ones in the morning or night.