The term wagasa (和傘) refers to umbrellas made in accordance with traditions on design, materials, or both.
Traditionally, Japanese umbrellas are made using bamboo sticks and Japanese paper. More modern materials and techniques are now used to manufacture products with an even longer life span.
Wagasa is not seen as frequently as in the past, substituted by the cheaper Western-style plastic umbrella for daily use. Nonetheless, it still is considered the proper accessory when wearing traditional clothes such as a kimono.
Overview
A wagasa is usually easily recognizable thanks to the simple decorations, the straight top silhouette, and the high number of ribs. It is different from the traditional Chinese umbrella from which it is derived, in that it also features stretchers which allow it to be closed, as with Western umbrellas.
The standard wagasa design usually has a fixed number of ribs, called oyabone (親骨): 24 for simple, large-manufacture umbrellas, 44 for hand-made wagasa of high quality, and up to 54 ribs in case of high-end bangasa umbrellas. The traditional wagasa is characterized by a straight oblique top line and and a straight handle. In comparison, Western umbrellas can have between 6 and 24 ribs, with 8 ribs being the most common, and they have a curved top line and handle.
Although the most iconic wagasa sports a compact red color, more common decorations include circles, spirals, sakura petals and flowers, and leaves.
Origin
The Japanese-style umbrella has its roots in the Chinese-style umbrella, which was imported to Japan about the same time as the Chinese characters (kanji). At that time, it was more similar to a static, still parasol with no mechanism to be opened or closed. It was not until the 16th century that manufacturers developed such mechanism, making it a largely more convenient object to carry and use only when necessary.
Since then, and for a few centuries, wagasa was the only type of umbrella known to the Japanese public, until the Western umbrella was introduced to Japan. As the new type of umbrella was easier and cheaper to manufacture, the traditional wagasa gradually fell out of fashion, and is now only used on few occasions, such as when wearing kimono, in kabuki plays, and other scenarios where formality and a sense of tradition are required – such as formal tea ceremonies.
Production fell so low that there are very few manufacturers of wagasa for actual use in Japan. Most of the umbrellas that can be found at souvenir shops are imitations, often made in China (as of July 2020). Those are not suited for use on rainy days, nor for sunny days as parasols: they will quickly melt in rain or discolour and break down under the sun.

Authenticity
There are a few required features for a Japanese umbrella to be considered an authentic wagasa.
• It must be designed and hand-made in Japan.
• It must have at least 44 ribs.
• It must feature a design that is based on the original, straight-top-lined Japanese umbrella.
Although the traditional wagasa is made using bamboo sticks and paper steeped in oil, modern materials such as plastics and metals can be used without compromising the product's authenticity, as long the requirements mentioned are met.
An example of modern wagasa that keeps its authenticity is the umbrella produced by Kiwakoto, designed and made in Kyoto by a wagasa artisan.
Did you know?
Companies that are at the same time traditional and modern, such as Ebisu beer, often use wagasa to advertise their products along with other similarly ambivalent daily goods (often fans and tissues.) Also, as paper allows infinite possibilities as to its decorations, many custom-made umbrellas feature anime characters and other popular themes such as One Piece and Hello Kitty. These are not likely to be sported on formal occasions, but they may be a fun way to enjoy an authentic piece of Japanese tradition.