He is a commander at Interstellar Immigration. He has had past relations with Haruko, similar to that of Naota's.
Commander Amarao works for the department of Interstellar Immigration. This agency, among other things, acts as a middle man for negotiations between the government and Medical Mechanica. Thus, Haruko/Raharu is a big problem for them as she is bent on provoking an attack by disrupting communications. Amarao has fake eyebrows made of nori which he believes serve the dual purpose of making him look macho and protecting him from N.O. Amarao seems to have had a past relationship with Haruko similar to Naota's.
In the first episode he appears in (the 4th episode of the series), the viewers get the impression that he is virtually an omniscient character, giving background information as well as making fairly accurate predictions. However, subsequent events would show him as extremely weak and very limited in foresight.
It is a likely inference from the story that as a child he was approached by Haruko/Raharu, just like Naota, and she tried using his N.O. to contact/capture Atomsk. However, his N.O. channel is so weak that he can barely pull something the size of a slingshot through. When the prior happens in episode 5, Haruko says "Small, as usual.", again suggesting a previous relationship between the two, or that she has tried it with other men. One could also argue that a youthful entanglement with Haruko could have led to his career with Interstellar Immigration. There are some traces of him feeling jealous that Haruko has chosen Naota over him.
He has a love of sickeningly sweet candy and drinks, and hates spicy, sour, and pulpy foods - much like Naota. His vehicle of choice is a Fuji Rabbit, a motor scooter which was produced initially in 1946 six months prior to the initial production of the Vespa. Given that throughout the series Amarao is constantly trying to impress Haruko, who rides a Vespa, one could conclude his ownership of a scooter is further manifestation of his attempts to impress her - or at very least a signal to the level at which Haruko influenced him in his youth.