A shadow is only as good as the surface it falls on. If your model uses flat "Toon" shading, shadows will look like cel-shaded stickers.
Use MMD's built-in Shadow Setting (Q) in the View menu. A lower distance typically makes shadows more crisp, while a higher distance covers the whole stage but may reduce precision. Troubleshooting Common Issues mmd excellent shadow
The effect changes this entirely. It utilizes advanced rendering techniques—specifically Percentage-Closer Filtering (PCF) and sometimes Screen Space Ambient Occlusion (SSAO) —to blur shadow edges, calculate ambient light interference, and simulate the way light wraps around a 3D object. In short, it stops your models from looking like they are floating in a void and grounds them in their environment. A shadow is only as good as the surface it falls on