RPG Maker MV

RPG Maker MV

How did this guy do this?? (MV3D First Person w/ Mouse Control)
https://www.youtube.com/watch?v=v_fyRTqgftM
https://www.youtube.com/watch?v=GDGuXrgyiCQ
https://www.youtube.com/watch?v=KcsdvXplZFg

I'm looking to replicate all of this in some way. How did this guy get camera movement with the mouse?