my pen, in bold

The pen I use to write my letters and postcards is a Japanese ballpoint pen produced by Mitsubishi Pencil. The pen is marked on the barrel 'for office and address writing' ​(in bold, black, waterproof).

What I like most about it is that the ink comes out smoothly. As I studied Japanese calligraphy, I prefer to hold the pen lightly and let the writing flow.

By the way, does the colour of the ink have any meaning to you? In Japan it is common to use black ink for everything. Blue is not used.