Retard Units is an unofficial synonym for "imperial measurements". As the rest of the world use metrics, the internet culture started mocking the medieval traditions of the Americans, and how little sense the usage of imperials pose compared to metrics.
Space begins 100 kilometers from the earth, that's 62,14 miles in Retard Units.
"Basically, last couple of months, mangas started to do progress and all that, instead of the broing stalemate
Somebkdy associated this new age of progression to the reiwa, and from that came reiwa energy and reiwa era of manga
Basically, when progress, romance or other things happen, then its called reiwa energy" -u/Acronym_0
"REIWA ENERGY!!!"
Following the confession of the main character to their love interest.
The 'Reiwa Era' expression is, in short, used for when progress is made in a manga towards a relationship.