As the title suggest, Twins Paul and Eru gets close after being separated for eight long years (Six if it wasn't for Paul's volunteering two more years under the Japanese Self Defense Force.)
if you want more info:
As a mutant, back in year 2000, it is necessary to train under the JSDF to counter attacks made by giant monsters/kaijus. However, around year 2004, kaiju attacks lessen and this law was reformed.
Paul, however, felt it was necessary to serve for another two years since he's not well adjusted to a life outside the military. However, after this added years, he must retire as mentioned on the reformed law whether it is his or against his will. (applicable only for those who joined during 1960 to 2000.)
When he finally got out, Paul and Eru met for the first time after eight years...
fun fact: I do admire Lao Tzu's teachings.