and I will be your slave
It was admiration for a better martial artist, Toshiki told himself at first. It had struck him to his knees in awe as he saw Kazuki's form, saw his strikes, saw the smooth pattern of his strings and bells. It had made him vow his loyalty to the Prince of Terror, because that was one of the laws of the martial world, and whatever his father might say of him, Toshiki knew he had kept those laws. The better martial artist may have your love or your hatred, but you cannot deny his excellence.
Later, he decided it was more than that. It was respect for a gracious ruler. The Prince of Terror was also a kind and just man; he gave mercy, he showed pity, and yet at the same time he held his portion of the city firmly and without hesitation. His laws were certain and his ways were righteous. These things deserved Toshiki's respect; honour for honour given, loyalty for loyalty sworn.
But when he saw Kazuki bend the knee to Raitei, the frustrated bitterness that filled his heart with fire told him finally what it truly was. Love. Adoration. Worship. He could not accept that his Kazuki should kneel to anyone else. He was swept up on a wind of desire, burned by the lightnings of his passion. He could not bear it. He could not endure that the rest of Fuuga should be able to bear it. It was wrong. His Kazuki deserved better.
His Kazuki. The one who smiled at him and who made everything else worthless; his loyalty, his honour, his very heart. Nothing would matter so long as he could have his Kazuki to serve.
And when, last of all, he was promised Kazuki in exchange for all those things, he gave them willingly.