Chuuya was the strongest of the younger generation of aliens, maybe all of the aliens of the whole. That was partly due to his ability, but also he was physically strong.

That meant he was assigned the most trouble-making of the humans.

Osamu Dazai, a human who could cancel out abilities.

Some humans had abilities, but not the entire race. That meant the aliens, who easily outnumbered them and all had abilities, were able to easily take over.

But this was the only one, out of either races, who could cancel out abilites. A human, the weaker race.

Of course, Chuuya came to pick Dazai up in the holding chamber, which were areas where they wrangled unknown species into shock collars with leashes attached, just to protect their own race from harm from unknown lifeforms.

Japanese had not yet been decoded, so they couldn't communicate.