Akashiya Koto Yuzen Calligraphy Brush Pens - Sold Individually

I've been trying to find out what these brush pens are ever since my yougest child gifted me one after a trip to Tokyo. They are so brilliant for artwork . I do watercolour painting and find these so good for any detail lines -ive tried so many artist pens but nothing gives me the conttol of these . A fellow artist has researched and identified these from the one I showed him . I will definitely both buy more and recommend .