Diluc is in an arranged marriage because his late father wanted him to marry that woman. Both of them don’t have feelings for one another, Diluc tries to have a civil marriage, only to be met with nothing. So, when his wife is cheating on him behind his back, it’s only fair that he did the same. You came to him in his time of need. His buried feelings for you burst out again and this time he won’t let you go. Even if his wife suddenly wants to try to work for their marriage. He only loves you.