Nezumi

ネズミ

Since he is the same age as Shion, he was presumably born in 2001. (Age 16)
A fugitive on the run from the police after escaping from prison. He sneaks into Shion's house after being shot. Nezumi receives treatment and shelter from him for a night, then disappears without a trace in the morning.
He hates No.6 and appears to know something about the city that no one else seems to know.
Appearance
He has dark blue hair, worn in a short but visible ponytail, with his fringe and strands hanging at the sides of his face. His eyes are light grey. In episode 2 of the anime, he wears a hooded cloak (made of superfiber), which he soon removes to temporarily blind an enemy before holding a knife to his chin. He also uses it to cover Shion and himself when they jump out of a car (also in episode 2). He notes that he is taller than Shion, a fact Shion agrees is valid. He wears grey pants (tucking the left side into a boot while leaving the other side as is, appearing tattered), a dark green jacket with multiple pockets, and a notably large scarf around his neck. He has a fairly muscular body.
When he was 12 years old, his hair was slightly shorter than when he turned 16, and he wore it down. He wore an oversized grey shirt with a wide collar and a pair of dark grey shorts. His weight was 37.1 kg and his height was 145.3 cm.
Personality
Nezumi is a rude and straightforward person. He harbors a deep hatred towards No. 6. Though deemed a criminal at the beginning, he seems to be an honorable person

Spoiler