sotsugyou M: the seiyuu
Okiayu Ryoutarou (whose poor name is often badly abused by the transliterating people both in Japan and in English speaking lands) is another seiyuu heavily involved in the neoromance scene, having been the voice of Akuram and then 
Hakuryuu in the HaruToki series of games and animated series/OVAs.
Consequently he has made appearances at Neoromance events, although nothing like as many as some seiyuu. Often he both sings and takes part in the various dramas.
Most recently he appeared in Haruka Matsuri 08 as "Hakuryuu", where he also performed the song "Banshou no Mamoribito" live (shall we say he sort of dressed the part - see picture...)
He has also voiced such well known characters as Shigure from Fruits Basket, Byakuya from Bleach, K from Gravitation and a whole bevy of others.
He did the voice of Nakago on the Fushigi Yuugi drama CDs and also played parts in Marginal Prince and Prince of Tennis. More recently he's been involved in Saiunkoku Monogatari as Kou Kurou.