Aim for the witness! The man who looks like a beautiful woman & the two dangerous people (Part 1)

Ryo is requested to guard Keiichi Kashiwagi, a witness in an important court case. Ryo resists until he is given a proposal to meet Keiichi's twin sister Keiko, to which Ryo gleefully accepts. But Keiichi is in fact Keiko, disguising herself as a man in order to thwart Ryo's advances.