I want a romance drama but the romance shouldn't be between ML and FL. i want romance between ML and SFL . and Between FL and SML.  i want ML and FL to just be friends/allies

Not exact fits, but maybe try:

  • Extraordinary Attorney Woo - Woo Young Woo is the FL. Lee Joon Ho is her male co-worker and love interest and Jung Myung Seok is her male boss / mentor / friend. Lee Joon Ho and Jung Myung Seok have similar amounts of screen time and importance to the plot.
  • Sassy Go Go - The romance is between the ML and FL, but the FL's best friend throughout the whole drama is a guy and their relationship remains platonic with neither side catching feelings, which is pretty rare. 
  • My Mister - It's not really a romance drama, but there are a lot of feelings... The ML has relationship troubles with his wife. There aren't many romantic moments between them, but (iirc) they do care about each other. The SML has complicated feelings for the FL, including romantic feelings that (iirc) the FL does not return. The relationship between the ML and FL is maybe the most complicated out of all of them. Some viewers interpret it as romantic but most (myself included) see it as platonic. They are coworkers that become allies and friends who care deeply about each other.

Also, not an asian drama, but Nimona just came out on Netflix. The ML and FL have a fantastic platonic relationship, and the ML's romance is with the SML. The ML is voiced by Riz Ahmed (British actor of Pakistani / Muhajir descent) and the SML is voiced by Eugene Lee Yang (American actor of Korean descent). 

 Ichika Kaneki:

I want a romance drama but the romance shouldn't be between ML and FL. i want romance between ML and SFL . and Between FL and SML.  i want ML and FL to just be friends/allies

Maybe "Love Alarm 2 " is a good option. But to understand the story maybe you have to see the first season too. Not sure tho :)

 AH :
The romance is between the ML and FL, but the FL's best friend throughout the whole drama is a guy and their relationship remains platonic with neither side catching feelings, which is pretty rare. 

i had scene this long time ago!! this deffo counts as what i asked for since all of them can fall under "main character category"
thank you so much!! ill rewatch

 Ichika Kaneki:
this deffo counts as what i asked for since all of them can fall under "main character category"
thank you so much!! ill rewatch

Oh good. In that case I'll also mention The Beauty Inside, which has a similar dynamic. The romance is between the ML and the FL, and the FL's two best friends are secondary main characters. One of those best friends is a guy (Ryu Eun Ho). Like Ha Dong Jae from Sassy Go Go, his relationship with the FL remains platonic and his romantic interest is a secondary female character.