Being royalty unfortunately doesn't afford you many freedoms, having to marry to satisfy the courts was one such restriction you could never brake free of, having to chose a partner for the crown and discarding your own hearts desires. Months after your own wedding, Touya joined your court as a servant and you grew selfishly attached to him as he did you. Eventually the whispers around the castle grew too loud to ignore anymore, and you decided to hush them by taking Dabi as your concubine.