Chasen-mage is a hairstyle which looks like a tea whisk. There are two kinds of chasen-mage, namely the one which was popular among men around the Azuchi-Momoyama period and another worn by women in the Edo period.
Chasen-mage (For Men)
It was a mage (hairstyle) that was popular among young men during the Azuchi-Momoyama period. It appeared in the end of Muromachi period and disappeared in the early Edo period.
As it was a mage for young men, it was done up, while leaving bangs as they were, through the process of either making a very narrow sakayaki (shaved part of the forehead) or not making it, tying the hair of the back of the head utilizing a flat braid and loosening the tip of hair. Sakayaki became wider over time, and a hairstyle that has wide sakayaki with bangs been cut off is the hairstyle of so-called 'Baka Tono' (parody of a feudal lord). Though the above is exaggerated since it is a mage of a comedy character, there seems to have been some disgraceful young feudal lords who actually wore such a hairstyle.
Here it may remind you of Kipposhi ODA (Nobunaga ODA in his youth) who was dubbed as 'Owari's Great Fool.'
Along with hanbakama (short hakama) made of leopard pelt and an obi (sash) like a rope of monkey trainer, chasen-mage (hairstyle like a tea whisk) that was made up high with a light green flat braid were the elements of his bizarre appearance.
Young men who lived in idleness wearing peculiar clothes like those of Nobunaga called themselves 'kabukimono' (the eccentric), and they competed each other the eccentricity of their costumes and performances. A flamboyant hairstyle was one of such eccentricities, but 'kabukimono' as well as their eccentric costumes and hairstyles came into obscurity when the Edo bakufu was established and the society became stable.
Chasen-mage (For women)
It was a mage in the Edo period. It was a hairstyle mainly for widows of daimyo (feudal lords) and samurai. As a proof of their idea of chastity like 'no virtuous widow remarries,' they cut the tip of mage to express their determination that they would never do their hair for the sake of new husbands.
On the other hand, this hairstyle didn't spread among the women of merchants and artisans under the situation, especially in the early Edo period, where the population gap between men and women was so big that the bakufu encouraged remarriage.