I have been selecting inks for regular writing for some time. I tried SAILOR, Noodler’s Ink. They do are waterproof. But none of them could resist my highlighter.

And recently, I tried ink from PARKER and PILOT which is not waterproof. But they turn out to be highlighter-proof.

Here’s the waterproof test:

Here’s the highlighter-proof test:

So as a result, I fill one pen with ink from PILOT, and two with ink from SAILOR. And after running out of SAILOR, I will try Pelikan 4001 which is out of options as it’s not waterproof.