Shion is a tannish-skinned young girl with short curly hair (she is affectionately called pube head by the others due to her hair, something which she dislikes) and brown eyes. She is often seen wearing her school uniform, but also her free time clothes.
Shion talks to Hiro Shishigami and confesses after she witness him save Naoyuki Ando. Eventually, after Hiro flees from the police, she picks him up and lets him live with her and her grandma, while refusing to believe he is a murderer.
She eventually finds out he is the murderer, but somehow manages to convince him to become a good person. This last for a while, before the swat team shoots her and her grandma, leaving them gravely wounded. Though, they reappear just fine with them noticing that Hiro leaves money in their bank account.
- The name Shion means "Aster tataricus", a type of flower. According to Japanese floriography, it means "I won't forget you" or "remembrance'". The name Shion contains the Japanese word for "tide" (潮 shio).
- Shion's surname Watanabe means "cross, ferry" (wataru) and "edge, side" (be).