Actually the seal says "智子.隨身保命" (Tomoko. Sui Shen Bao Ming), meaning "by A's side and protect B's life", where A and B are not specified and can refer to the same person. Since the seal on a jian-shi serves command (or prohibition), it's more likely that Yuri jian-shi is to stay by Tomoko's side to protect Tomoko's life. Another possible reason for Yuri to dressed as jian-shi for this Halloween campaign is that jian-shi is known for its stiffness and strength.