ガールフレンド is wrong you can not search another Girl Friend BETA's Doujinshi in unicode ガ = u30abu3099 it is two characters Combine ド = u30c8u3099 correct ガ in unicode is u30ac ,ド = u30c9 so ガールフレンド is right
use windows10+Asian systems+firefox You can see very clearly the difference between the two http://i.imgur.com/EBaIRNe.jpg