I love pens! I'm a pen addict. I'm also very finicky when it comes to the pens I use. My go to site for buying Japanese pens is Jetpens!
I love the multi pen system and my go to brand is the Uni Style-fit. My personal favorite is the gel ink line and nib size 0.28 which is super fine and gives a clean line. I also love the color options. I used different colors in my planner to list different people's tasks.
For outlining in a thicker stroke, I like the Staedtler Fineliner. I use this pen to go over and outline over my Uni Style-fit pens. I use the black and brown versions (they match the Uni Style-fit colors perfectly).
I have recently tried out brush pens for drawing. The two I currently use are the Pentel Brush Pen and the Tombow Fudenosuke Brush Pen (hard). I actually like both and although they are both brush pens, the results are very different.
The Pentel Brush Pen is very much like drawing with a brush and ink. You can get very thin lines and with more pressure get nice thick lines. The ink is very dark too. The one drawback is that this is not an easy pen to get the hang of, you need to practice. The control isn't as tight as the Tombow. Another thing to note is that this pen is refillable and the refills are really affordable.
The Tombow Fudenosuke (hard version) has a much firmer nib than the Pentel. It actually seems more like a pointed felt nib but I'm not sure. You can achieve a brush-like stroke but it's tighter and you need to press harder to get a thick line. The nib is shorter than the Pentel so ultimately the thickness of the line you can get is much thinner than the Pentel. The good thing about the Fudenosuke is that it is easier to control you line widths seeing that the nib is much more firmer. These are non-refillable but fairly cheap. This pen also comes in a soft and grey version (grey version has dual ends, one end black and one end grey ink).
Jetpens is not just a source for pens, they also have an array of other items like notebooks, bags and office and craft supplies. The prices are really reasonable for specialty items from Japan and they offer free shipping for orders over $25.
Here are more examples of work I've done with my pens:
*update - Sorry I forgot to mention all the brush pen sketches below were done with my Pentel Brush pen. Haven't had the time to scan in any of my Tombow Fudenosuke brush pen drawings yet.
* please note that the written comments and opinions are my own and not paid or solicited.