The game is made on the same engine as Senran Kagura: Shinovi Versus, so the same settings can be applied here to make the game look much sharper.

Download Nvidia Profile Inspector[github.com], create a new profile for Neptunia.exe, then set the following options:
Antialiasing compatibility: 0x004412C1 (Diablo III)
Antialiasing - Mode: Override any application setting
Antialiasing - Setting: 4x4 [4x4 Supersampling (D3D only)]
Anisotropic filtering setting: 16x

Do you only see a black screen with background sounds when the game tries to play a video? Here's how to fix this.

First, set the game to Windows 8 compatibility mode:
- Right-click on the game in your Steam library
- Manage -> Browse local files
- Right-click on Neptunia.exe
- Compatibility -> Run this program in compatibility mode for -> Windows 8

Then, press WinKey + R, type regedit, press Enter and browse to the following path:
HKEY_CURRENT_USER\Software\Microsoft\Direct3D\Shims\EnableOverlays

Then delete the entry for the game. As long as the game is kept in Windows 8 compatibility mode this entry won't be added again.