Complex sentence: Stubborn, proud and hot-headed, Hikari never backs down from a challenge, especially one from Kei, because she is constantly looking for an opportunity to surpass him, though has never done so.
Split into simpler sentences: Stubborn, proud and hot-headed, Hikari never backs down from a challenge, especially one from Kei. This is because she is constantly looking for an opportunity to surpass him, though she has never done so.