Reddit mentions of Sailor Kiwa-Guro Pigmented Black Ink Bottle

Sailor Kiwa Guro and there is also Sailor Sei Boku which is the blue black version.

Depending on what you consider "budget", I would strongly recommend the Platinum 3776 Century line of pens as your everyday carry.

Leakage: The pens have a "slip & seal" mechanism which prevents the ink from drying out. Obviously, liquids do not behave in the same manner as air, but I'd assume that the double seal (of both a screw cap and the slip & seal) would greatly reduce the chance of leakage. I can attest to the effectiveness of this mechanism. Just yesterday, I uncapped a Platinum 3776 that had been sitting on my desk for over half a year and it wrote perfectly on the first stroke!

Additionally, if you're really concerned, I would also put a tiny amount of silicone grease on the threads of the pen (a mere smidgen is all that's required) to give you more peace of mind.

Appearances: The Platinum 3776 Century Black Diamond is a very classic-looking pen. It's not pretentious at all, the trim is beautiful, and it's got a nice-to-hold body. Paired with a nice, super-black, well-behaved ink like Sailor's Kiwa-Guro ink, I think that's a winning combination.

Let me know if you want to see a demo of the pen and ink combo and when I get home tonight, I'll put it together and take some pictures for you.

I mentioned this last time, too, but just in case folks didn't see:

Kiwa-Guro is identical in every way to Platinum Carbon Black. They're both super dark, pigmented, no shading at all, completely waterproof blacks--honestly, it's impossible to tell them apart on the page, and there were no significant differences in terms of flow, dry-time, or feathering.

Platinum is a bit cheaper per ml (60ml instead of the Sailor's 50ml): Amazon has the Platinum for $22 while Kiwa-Guro is $19. It's a difference of only $0.02/ml, but if that's your thing, it's good to know. Personally, I prefer filling in the Platinum bottle (Sailor's insert is just a hair too short for larger nibbed pens)--but you can't go wrong with either. They're both superb inks.

You're looking for "permanent" ink. Ink may be permanent in different ways and they all have different pros and cons. I prefer pigmented inks as they usually dry quickly (other permanent inks may take some time) and don't feather (spread) even on cheap paper. The ones I recommend are Sailor Sei-Boku and Sailor Kiwa-Guro.

You might already be aware, but please note: don't ever put india ink in a fountain pen unless you want a bad time! India ink will almost certainly clog up a pen (with shellac & other stuff), that's why specialized (more viscous) fountain pen inks exist! Anyway...

For brushes:
I went on quest to find the darkest, flattest, quickest to dry, and matte (no shiny shellac in this bottle) ink! What I found was Dr Martins Hi-Carb Black Star India Ink. This ink always dries without a hint of gradation, perfect for inking comics! OOh I love this ink.

For fountain pens:
After years of loving Noodler's Heart of Darkness ink (it's just so black!), I found something better last summer: Sailor Kiwa-Guro. My god, no words, it's hard to describe, and while it does dry a little slow, it DOESN'T BLEED EVER! Google image searches might help.

Anyway, uh, I love water based inks, can you tell ;)? I hope you find some favorites. My tastes are for ultra hi-contrast, but everyone is different. And oil based inks are another matter altogether...

P.S. My favorite travel brush pen is this guy. It's disposable and a little on the dry side, but the ink quality is fantastic. Out of the twelve or so brush pens I've tried, this is the only one I personally enjoy using. I notice jetpens has a 5pen sampler pack, you might wanna try that out.