Hiroaki is the "hero" of the story. Is a very big guy, almost two meters tall. He is very good as a soldier, but some times, he is very absentminded. He tries to not be worried about anything and some times that idea makes him some problems. His parents died when he was very young, so he lived his childhood in an orfanatory. He is trying to become a warrior from the elite force "Trident Division" and during his training, he knows Karen's father, Captain Ichijo Isuma. The Captain is impressed, not for the abilities of Hiroaki, yet by the great spirit that he shows during the training, trying and trying, even when things are not going well for the cadet. Hiroaki and Captain Isuma become great friends with the time, and in the first part of the story, he saves the Captain and Karen from being kidnapped. After the invasion of the aliens, Hiroaki finds Karen, now with 14 years old, living alone after her fathers dead. He invites her to travel with him and he knows that now she is his responsibility. With 23 years old, he tries to keep Karen's safety, and some times, he overprotects her, thing that some times Karen will see as jealous from him. Hiroaki sees Karen just as the little daughter of his friend, Captain Isuma, but Karen will try to catch his heart, every time she can.