Complex sentence: When Nyu is attacked violently (or hit on the head), she regresses into Lucy; likewise, when Lucy is treated with love and kindness, or wants to hide herself from Kohta, she will change back into Nyu.
Split into simpler sentences: When Nyu is attacked violently (or hit on the head), she regresses into Lucy. Likewise, when Lucy is treated with love and kindness, or wants to hide herself from Kohta, she will change back into Nyu.