^Both of them are
taken from Ogura Yui's official site work page ...
【アニメ】
■MBS、TOKYO MX他「さくら荘のペットな彼女」(神田優子役)
Horie Yui does have the more noticeable role by far though, and no she voiced one of the main character's AI interface program not the actual (male) character but since he pretty much doesn't speak at all it counts i guess
Other notable shounen character voiced by female seiyuu
-Elric brothers from FMA, Edward is voiced by Paku Romi and Alphonse is voiced by Kugimiya Rie.
Paku Romi can definitely work a boy's voice she has done it many times (hitsugaya in bleach, ueki from law of ueki, naoto in Persona 4)
Ishihara kaori meanwhile ... well i'm just not buying it yet, then again Al is the only odd role in Kugimiya Rie's resume too so ultimately i guess i'm ok with this