k-drama 2023-2025, no 2nd female lead

I assumed you mean ml never fall for another woman after meeting fl.

• As Beautiful As You (unrequited love since college)
• Best Choice Ever (quite sure ml falls first)
• Marry My Husband (ml likes fl since high school after feeding the same cat)
• Only for Love (quite sure it's love at first sight but he gets more attracted after knowing her work ethic)
• The Love You Give Me (I'm not sure who falls first but it's a good one)
• To The Moon and Back (ml falls first)
• Upcoming Jiao Yang Si Wo adapted from Gu Man's Blazing Sunlight (ml falls first since meeting fl in a party)