Rakkyosai

One day a young man arrives in Nerima and is found stealing panties, just like Happosai. The boy's name is Rakkyosai (also frequently translated as Lukkosai), and he shares quite a few of Happosai's less desirable traits. Soon Happosai takes the young man on as his new pupil and the two dash through the streets wreaking havoc and stealing underwear.

Before long Rakkyosai's true identity is revealed, he is actually an old friend of Happosai's who fell into the Spring of Drowned Young Man at Jusenkyo. He has been after Happosai for years in an attempt to get some magical ink to complete his ultimate technique, the Kocho Ranbu.

As it turns out Lucky and Happy as they call one another were friends nearly 100 years ago in China. Happosai betrayed Rakkyosai in order to steal his Brocade Butterfly, a stick of multicolored ink that Lucky expertly uses in his attacks.

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The Meaning Behind the Name - 楽京斎

The first character in Rakkyosai's name means "music, comfort, ease" the second character is "capital" and the third is "avoid". So "to avoid comfort or ease". The "sai" character in his name is the same as in "Happosai".