Happo means eight directions. Bijin literally means a beautiful woman. A person who wants to look attractive in eight different directions is a person trying too hard to please everyone, thus revealing a lack of integrity.
(Style: spoken/casual (blunt)/male)
A: Akio no yatsu, kyooryoku shite kureru tte. Saisho wa iya da tte itta n da kedo sa.
B: Iya, aitsu wa happoo bijin da kara, ate ni naranai yo.
A: Akio says he’ll help us. He said he didn’t want to at first, though.
B: Well, he’s the type who tries to please everyone, so you really can’t count on him.