Inquiry regarding direct insurance for a used car

I am planning to sign up for direct insurance for a used car myself, without going through an agent.
If I sign up through an agent, the premium comes out to about 1.05 million KRW, but when I calculate it online without an agent, it comes out to about 1.53 million KRW;;
Of course, the 1.53 million KRW figure was calculated without reflecting my driving history/insurance experience certificate for over 3 years.
Would it be more cost-effective to sign up through an agent instead?
I would appreciate any expert advice from those who are knowledgeable about auto insurance.