I think you should try My Mister- it's exactly as you wrote, leads get to know each other and become friends, it doesn't have romance but it's objectively the best drama I have watched
Another one that I think you might like is Hello Monster- FL is a cop and ML genius profiler and they solve crimes and try to catch a serial killer, they become friends and slowly fall in love but it has only little bit of romance
Other recommendations:
Coffee Prince- if you haven't watched this already you must !!! Leads at first both like someone else and then they become friends, it also has romance and it's funny and heartwarming drama with great cast
Dal Ja's Spring- FL has another love interest at first so with ML they are only friends, after some time they develop feelings for each other but it's slow paced romance