Highlighted: where the king and rook start and land.
Weirdest castling #4
SP-458 · rnnkbbqr
O-O-O · K d1→c1 · R a1→d1
72 of the 960 starts castle exactly this way.
Destinations are fixed in Chess960 (kingside K→g1 R→f1, queenside K→c1 R→d1); only the starting squares differ.