The first world to which Ethan and the gang will be going will be the world of High School of the dead.
Which two girls do you want to add to Ethan's Harem, excluding Yuriko(Saya's mother), Saeko Busujima, and one from another girl from a different anime (clue: Have giant fighting machines in them)
Your options are as followed.
a) Shizuka Marikawa
b) Rika Mrikawa
c) Saya
d) Hana Takashi (Komuro's Mother)