What does the Quran say about an emotional relationship between a man and a woman that cannot culminate in marriage due to a loss of mutual respect?

The verses (An-Nisa 25 and Al-Ma'idah 5) emphasize the importance of chastity for both genders in marriage, stipulating that women must be chaste, not lewd, nor taking secret lovers, and that men must be chaste, not lewd, nor taking secret lovers. Ibn Kathir explains that "chaste women" (al-muhsanat) means women who are virtuous and do not commit fornication openly or secretly, and "lewd women" (al-musafihat) are those who openly commit fornication, and "taking secret lovers" (mutakhidhat akhdan) refers to those who have a single secret lover. Similarly, he explains that "chaste men" (al-muhsinin) are virtuous, "lewd men" (al-musafihin) are fornicators, and "taking secret lovers" (mutakhidhi akhdan) refers to those who have secret mistresses. Imam Ahmad was of the opinion that marriage to an unchaste woman or a wicked man is not valid until they repent. The story of Marthad bin Abi Marthad with Anaqa and the Hadith (definition) "An adulterer does not marry except an adulteress or an idolatress, and an adulteress is not married except by an adulterer or an idolater" confirm the prohibition of a chaste person marrying an unchaste person, or vice versa. The story of the woman who repented in the جاهلية (pre-Islamic era) illustrates the virtue of repentance. These texts indicate the unlawfulness of establishing relationships and friendships between non-mahram (definition) men and women, due to the corrupting influences therein.