I feel like they shot themselves in the foot a bit with this announcement, because everywhere I see people who haven't realised that it's a double announcement and think it's just that 'Ultraman Regulos: The First Mission,' which has already been on Ultraman Connection since December, is being put onto youtube.
There's a completely brand new mini-series called simply Ultraman Regulos, which is an origin story prequel. It's six episodes long being released over a four week period. Ultraman Connection also gets compilation versions collecting together the first three and last three episodes.
Then after that they are putting the (previously exclusive) two-part special onto youtube.