Hero Class is the new class added to Episode 5 and is an advanced class.
The original Japanese requirement was skipped for North America so instead of 3 unique class titles at Episode 5s launch you only need 2 classes at Level 75 (in the screenshot I went above and beyond and did all the OG JP requirements for just in-case they didn't skip this part of the game, however due to trying to reach parity with JP they have sped up a lot of things)
Once you pick up your titles from the title counter Cofy will have a Client Order for you
The Client Order is to Obtain the Title "To The New Frontier" which will be available at the Title Counter once you have your two classes 75 (which is two titles in itself)
Once you have claimed everything from the title counter, return to Cofy and turn in the Client Order.
This unlocks Hero Class
Now you can speak to the class consultant and switch to Hero Class. You don't need to level this one up. The achievement is simply Equipping this Class
EDIT: Sorry I haven't had free time to make a proper video explanation of how I reached 75, I used my phone and edited the whole video that way using Xbox Recorded clips. I quickly go over each step so if I moved too fast for you please leave a comment below and I'll explain any step you need help with.
This video is how I earned 1 Level a day leading up to Episode 5.