EDIT: (Please see later posts, this post links Yanfly's Picture Common Events, the actual plugin needed is Yanfly's Grid Free Doodads)
http://yanfly.moe/2016/04/01/yep-88-picture-common-events/
This is a link to Yanfly's Picture Common Events plugin. What's interesting about this plugin is that it adds properties to the TouchInput object
for the x and y position of the mouse.
After enabling the plugin, you'll have access to the following script commands:
TouchInput._mouseOverX
and
TouchInput._mouseOverY
These two properties can tell you the current position of the cursor on screen.
Also, if you don't already know, the following code will detect the width and height of a user's display area
Graphics.width
Graphics.height
Yanfly's link at the top of this reply doesn't mention (that I see) if this plugin has any dependencies. In general, many of those plugins require the Yanfly Core, but atm I have quite a few Yanfly scripts enabled and disabling the core causes quite a few bugs, so I haven't tested that.
Either way, with the width/height of a user's display area, and the cursor X/Y, you can easily set up events to occur based off of the mouse's movement.
I hope this helps, don't hesitate to ask if you need more assistance, or if this doesn't quite make sense for you.
EDIT:
Also, if you didn't know, TouchInput.x and TouchInput.y will return the LAST clicked position on screen, which can assist you in moving the player if needed, although initially your post says it would be first person. Toward the end however, it does mention moving a player, so just in case you need to know...
You can, using a JS Math function and the tile size for your game, do something like this (for example if you have standard 48x48 tile size settings):
Math.floor(TouchInput._mouseOverX / 48)
This will return an x coordinate that a sprite could move to, if needed.
TouchInput essentially returns pixel coordinates, which won't be useful if you're moving an actual sprite as opposed to simply scrolling the screen in response to the pixel coordinates of your mouse, so it's necessary to divide by the tile size, and then round down.