Koo Jeong-a makes art from what people usually fail to notice: the lingering trace of scent, a glow that emerges only after darkness falls and a crystal that flashes only when a viewer happens to stand in the right place. Her new solo exhibition at Leeum Museum of Art, “KOO JEONG A: OUSSSMOS,” turns that preoccupation into a museum-wide experience. On a rainy afternoon, the first challenge was simply to locate 50 crystals hidden in the dark gabion wall outside the gallery — a task that seemed designed to test whether looking is the same as seeing. In the work, titled “A Reality Upgrade & End Alone,” (2003/2026) the crystals refused to announce themselves. Only after shifting position and looking again did a small flash of light appear. That fleeting discovery — or the possibility of never finding it at all — is integral to her work. “Seeing is understanding,” Koo said at a press event Monday for her new exhibition. “I think seeing is knowing.” Yet the artist added that she cannot compel viewers to understand her works; she only hopes they will find their own way tow