Karappo – Japanese for empty – is an ingenious pen from Kuretake. By dipping one end of the supplied cotton swab in ink, you can easily absorb and use whatever ink you want.
By combining this with their Ink Café at Home kit you can also fill the pen with an ink that you mix all by yourself. Of course, it's also possible to use ink from your favorite ink bottle.
Fill the pen by dipping one end of the cotton swab in ink until it is approximately 80% full. Then insert the cotton swab into the pen and close with the stopper. The pen comes with two labels attached to both ends of the pen, so you can see which ink you used. Once the stopper has been clicked in, it cannot be removed.
This pen has a felt tip in fine. There's also a fineliner variant with a tip of 0.4 mm.