Hey New to the forum hopefully im posting in the right spot if there another spot I should post please let me know

Problem:

I have a 2006 Mazda 3 4Cyl DOHC 2.3 Liter non turbo sedan Auto with 319.000k miles and I have a leak on drivers side not near radiator above water outlet drivers side of block. you can put a allen head in it and its round. how do I go about fixing it ? what is it? I got car from a cop friend for $300 down the road from my place he doesn't know anything about it
Car shifts butter smooth like new and have a lot of power No SES codes / New coolant / New engine oil / New ATF /does (not) burn oil / No smoke Tail pipe / No oil leaks

I have attached a you tube video links below of issue

for this video it was some one else's not mine but has a better picture the round not square part with hex tool shape




let me know what you guys think

Zoom Zoom

 

Bump Help !

 

Bump again !
I feel surprised no on has input on my issum. im pretty sure the question ran across a few mind on this post
I really dont want to shell out a ton of money at a auto repair place
Sorry if im coming of a a ***** or rude im just baffled.
Could use some help

Thanks Zoom Zoom

 

Never seen the Hex key bung leak, but have seen the water outlet directly below it leak numerous times.

 

Im replacing that part right now! boy is it hard to do 1st time for me