Aobana is a colorant that originated in Japan and that has been in use for years.
Aobana, literally meaning blue flower, is obtained from the petals of perennial plants such as tsuyukusa (blue dayflower) and hotarugusa (firefly grass). The blue liquid is then applied to a paper which acts as a carrier for the colorant. Aobana is therefore called aobana-gami (aobana paper) or ai-gami (indigo paper) on some occasions.  Aobana colorant has been used to draw rough sketches, most often for sketching Yuuzen  patterns.
If you tear a small amount of aobana, place it on a plate and pour some water over it, the blue liquid will appear. This aobana colorant appears only on contact with moisture which makes it an ideal colorant for sketching.
The fleeting nature of aobana has been well recognized since ancient times, which is evidenced by an old waka poem:  “people’s minds are like the elusive blue dayflower that changes its color easily”.

Hashimoto Yakichi shouten is a craft studio that has for many years hand made koinobori or carp-shaped streamers. The studio opened in the 14th year of the Meiji period and now, as the third master, Takashi Hashimoto makes the koinobori. Hashimoto Yakichi shouten is the only studio that makes koinobori by hand in the Saitama prefecture Kazo area. Kazo is the foremost area for koinobori production in Japan. There are reasons for making koinobori by hand. The first reason is thata handcrafted koinobori ha an original "feel" that makes it different from a machine-made one. In addition to the special "feel", a hand-made koinobori uses special pigments that do not discolor easily. Moreover, a hand-made koinobori is made of nylon and not cotton because when it is raised, it looks more powerful. On the other hand, the studio's principle is "Changing tradition slightly is one way to maintain tradition". From this belief, the studio has been successfully creating koinobori that fit the demands of present-day society, in addition to the "bushuu" koinobori that have been continuously made since the studio was founded. Animated and powerful koinobori will be seen flying this year again, in many parts of Japan.