My only question is, what colour is the flag of ml?

Green

Also heard there's triangle? I'm not a fan of triangle

Not really a triangle , the second male lead (if you could call him that ) has one sided feelings for the female lead , don't worry you won't feel sorry for him he is quite delusional . but that's all it's a really good story you should go for it ~

Alright thank you ε=ε=(ノ≧∇≦)ノ

You're welcome ~~