Kokoa attacks Outer Moka to force her to transform. Even so, she loves her and considers her a sister. In the anime, she is constantly trying to find ways to remove her Rosario and get her to stay as the Inner Moka.
Kokoa loves the Inner Moka deeply and calls Inner Moka her real sister. When they were younger, she is constantly trying to beat her in a fight, but always loses
Kokoa has been afraid of Kalua since she was a child and would never play with her. When reuniting with her in The land of the Snow Fairies, though hostile towards her, she showed extreme fear. However,she does love Kahlua deep down as she cried while delivering the final blow and was visibly deeply saddened and reduced to tears when she died.
Kokoa probably fears Akua more than Kahlua,altough she is not at all traumatized by Akua's strength unlike Kahlua.
How Akua regards Kokoa is not clear,but while she apparently was kind and civil to her,when they met again in the present,she coldly gazed at her and her friends as if taunting them. However,they neverthless worked effectively against Alucard but aside from this,they have not yet interacted one on one.
Kokoa finds Tsukune to be the main reason Moka(outer) is weak. She is shown to be envious of him when he recieves training from Inner Moka. In the anime, she hates him because Moka gives him everything.
Kokoa hates it when Kurumu treats her like a little girl. When it comes to Gin though she'll team up with Kurumu and Mizore to attack him. She shows some respect for her.
Kokoa and Yukari can relate to many things like hate being taunted on their age, their love for Moka, etc.. Yukari is one of the people she can confide to and is probably her closest friend.
Like Kurumu, Mizore treats Kokoa like a little girl. Kokoa finds Mizore to be creepy.
Kokoa harbors a deep hatred for him for him being a huge lolicon pervert. While heading to Faory Tale's HQ, she thanks him for training her. Taking advantage, he tries to get her to kiss him on the cheek, only for her to stab him in the back, literally.