1) Shin, because he sincerely cares about the heroine's well-being. He is very kind, very smart and I also like his looks and his seiyuu.
2) Toma, because I like his looks, seiyuu and have deep interest in yandere characters.
3) Ikki. Cool looks, cool voice, but he is a womanizer, I hate this quality in men. Also, a bunch of murderous fans isn't a good addition to any relationship.
4) Ukyo. I love everything about his sane version, but his crazy version is a massive turn-off. I mean, who would want to date a guy who could kill you any moment?
5) Kent. I like intelligent men, but it always seemed to me that he has a robotic, inhuman air about him.