Either Shoujo Sect or Rin: Daughters of Mnemosyne. Shoujo Sect is more sex-based sexy and Rin: Daughters of Mnemosyne is like stereotypical or mainstreamed sexy.
3 sexy men from Real by Takehiko Inoue. This was probably the saddest manga I've ever read in my life. I cried in every volume... :( But it's a fantastic read!