Sometimes, Isang really wants to go back to his elementary school days. Just like the lyrics of "The vague memories of childhood, clouds floated in the blue sky", or the ancient poem "Walking to the poor water, sitting and watching the clouds rise", he was so leisurely and contented. He regarded his own small world as a small person in the whole world. Unknowingly, he has gradually realized that the big one is not our world, but the small one is us in the world.