I may as well elaborate before being asked. The Christmas/collar scenes in the visual novel are replaced with a hot springs scene. In the visual novel, the idea of exhibitionist sex in the hot springs is exciting, but they decide to retire back to their room before being caught. The Master/Slave...
I had no idea there was a manga version of this, too. It's mostly 1-to-1 with the Visual Novel (never translated to English as far as I know) but the ending is a little different.