Shuutaro Mendo is heir to the Mendou Zaibatsu with staggering wealth and its own private army. He commutes to school in a gigantic helicopter that is more like a flying mansion. Shuutaro carries a samurai sword which he often tries to use on Ataru (who has become expert at blocking it with his bare hands). Although very handsome he is just as stupid and lecherous as Ataru (just much more sophisticated in his approach). He takes his role as heir to the vast Mendou fortune extremely seriously. Mendou is vain, narcissistic, charming, overly dramatic, claustrophobic and afraid of the dark. He loves Lum, tolerating the presence of Ataru in order to be close to her. Shinobu is the closest thing he has to a girlfriend. (Source: Wikipedia)
In Japanese "Sakura" means "cherry blossom." She was once a very sickly girl who suffered from a variety of ailments. Many of them were the result of spirits that infested her body. On the advice of her uncle Cherry, she tried to exorcise Ataru, during which process, the demons who inhabited her transferred themselves to the unlucky young man. The second time she attempts to exorcise him, one of the demons possessing Ataru causes him to pounce onto her and suck her breast. Now in perfect health, Sakura is the Tomobiki High school nurse and a Shinto priestess or miko. Unlike her mother (who looks exactly like Cherry), Sakura is tall, slender and physically attractive, which makes her a common target of the lecherous boys of the school and even Mr. Onsen-Mark. The boys have been known to purposely injure themselves in order to see her. Like her uncle, she possesses an enormous appetite and has been known, despite never seeming to gain an ounce, to out-eat him. Sakura is extremely powerful and can summon foul and baleful creatures from Japanese folklore, by virtue of her mystical training. (Source: Wikipedia)
His nickname is derived from his hairstyle ("permanent"), he is tall and skinny (though his nameless Manga counterpart had quite a fatter form). Perm often displays the most character development, including being the only one of the Stormtroopers to have a visible girlfriend.
Blueno started his own bar about five years ago in the backstreets of Water Seven, calling it simply "Blueno's Bar." It was in a seedy side of town, where vagrants and ne'erdowells coalesced, but he at least acted happy. In truth, alas, it wasn't so: Blueno was a covert agent of the government's sent to steal the plans to an Ancient Weapon. It was in this fashion that Blueno met the supposed hidden king of Water Seven, Franky, and the two struck up a friendship of sorts. Again, it wasn't really so, but that friendship had some repercussions later on. Blueno ate the Doa Doa no Mi (Door Door Fruit) which allows him to create doors on any surface. He has even created "air doors", doors in the air itself, which lead to what seems to be another dimension. Blueno is also able to create doors on people, and did so to Luffy's face, causing it to spin like a revolving door. Blueno's tekkai seems to be the one of the more powerful ones of the group, and he was the first to reveal any variations of the move. Source: http://arlongpark.net/
Ataru's childhood friend and classmate. Until Lum showed up she was also Ataru’s girlfriend. She is a neat, clean, sweet, and petite young lady who can be viewed as the archetypically perfect Japanese female. Not long after Lum showed up Shinobu began to develop super-human strength. She like all female members of her class has a huge crush on Mendou. She is often part of a "foursome" consisting of Ataru, Lum, Shuutaro, and herself. By the end of the series, she'd given up on Shuutaro, thinking herself a likely "old maid", until she met a young boy named Inaba who sweeps her off her feet (eventually). (source:Wikipedia)
The leader of the Stormtroopers, whose nickname means "eyeglasses", he has a strong personality and generally directs the schemes of the Stormtroopers to gain Lum's attention (though mostly for himself). Though usually antagonistic towards Ataru, he often hangs out with him in his spare time. He is often given to rambling philosophical musings and outbursts, and seems to have an affinity for fascism and communism.