According to what I read the other girls are original characters named (茶子) Chako? and (黒子) Kuroko. Chako finds Aya to be cool and Kuroko is enamored with Momiji.

he names for the OCs seems to be provisiory. They refer to their hair color (Note: "茶" means "Light Brown" in this case). Furthermore, they are refered as sisters.

And their clothing? Same style as post #648029, post #726776 and post #800959 among others.

Are there any doujins, which contain these original characters?

marc46 said:
Are there any doujins, which contain these original characters?

This one.

CGrascal said:
According to what I read the other girls are original characters named (茶子) Chako? and (黒子) Kuroko. Chako finds Aya to be cool and Kuroko is enamored with Momiji.

And they all bully Hatate.