This example visualizes character interactions from a Chinese TV series as a multi-stage Sankey diagram, mapping connections across up to four hierarchical levels from individual characters to complex relationship chains. The SVG rendering uses a custom `d3.sankey` layout with `computeNodeBreadths`, `computeNodeDepths`, and `computeLinkDepths` functions to position nodes and curved links. Data from `demo.json` feeds the React-based visualization, with node heights and link thicknesses proportional to interaction frequencies. The diagram highlights dominant relationships, such as the strong connections among Fang Yifan, Ji Yangyang, and Li Meng.