He was known for voicing Walter C. Dornez in Hellsing, Gargoyle in Nadia: The Secret of Blue Water, Kōzō Fuyutsuki in Neon Genesis Evangelion, Valkenhayn R. Hellsing in Blazblue, and Tippy in Is the Order a Rabbit?.

Together, he and Reiko Yamada established the "Dramahouse Voice Actor School D.D.

[3] In anime, he was a frequent contributor to Hideaki Anno's works,[3] beginning with his role as Gargoyle in 1990's Nadia: The Secret of Blue Water and continuing with his role as Kōzō Fuyutsuki in Neon Genesis Evangelion.

[4] Therefore, when he was asked to play the antagonist Gargoyle in Nadia: The Secret of Blue Water, Kiyokawa suggested to director Anno, "Why don't we play the roles in such a way that it is not clear who is the bad guy?".

[4] After the deaths of Akio Miyabe, Kazumi Tanaka, Tatsuyuki Ishimori, and Ichiro Nagai, Kiyokawa took over some of their roles.