Blood type:
O

Chihiro, known as Hiro to his friends, is one of the minor characters along with Sakura and Nanami that were trapped in the Underground Channels after being penalized in the White Room. He was also part of the 11th Avenue.
His personality seems to be that he is very protective of Sakura, but it is also hinted that he may have some feelings for Sakura and greatly misunderstands Onigasaki's intentions towards her. He also the "Easy to Rile Type" according to Onigasaki's first impression of him.
The only thing known about his background was that he was trapped in the 11th Avenue along with Sakura, and then tried to get himself penalized so he could get to the White Room to accompany Sakura and together find a way out of here. Then, he and Sakura presumably found the tunnel and met Nanami; staying down there ever since.
(Source: Naka no Hito Genome Wiki, edited)