Chiharu Harukaze is a member of the student council. Secretly, under the alias of "Haruko", she works as Sakuya's maid. Although nobody in Hakuo is aware of that, in exception of Aika Kasumi, who found everything about her out soon enough. 

In the 3rd season she no longer works as a Sakuya's maid, instead she now works as a sales clerk in a video store. She is staying in Nagi's boarding house as one of the tenants.

Hayate Ayasaki's life wasn't great, but when he loses the job he used to support his good-for-nothing family, and his deadbeat parents sell him to the Yakuza for cash, it really hits rock bottom! Faced with having to pay off the huge debt before he's converted into black market organ parts, a desperate Hayate decides to kidnap oddball heiress Nagi Sanzenin for ransom... but when even that goes wrong and he accidentally ends up rescuing Nagi from other kidnappers, it turns out that Hayate is the bodyguard that Nagi has been looking for! So now he's the Sanzenin family's butler, and… maybe… it might be the start of a potential romantic relationship… assuming Hayate can survive the on-the-job training, of course. 
 
(Source: Sentai Filmworks)

Hayate Ayasaki's life has never been easy, though after being sold to Yakuza who want to harvest your organs to pay off your parents' debts it's hard to imagine things sinking much lower. But since becoming employed as the butler/bodyguard for teenage heiress Nagi Sanzenin, Hayate's misery has been primarily focused around Nagi's insecurity, laziness and the frequent attempts by various parties to kidnap her (with the occasional scheme cooked up by her Grandfather on the side.) However, when a new and unexpected relative arrives without warning, and issues concerning Nagi's long dead father rear their ugly head, Hayate finds himself thrust even further into the deep, dark, messy drama of the Sanzenin clan's affairs. And that is only the beginning of his troubles, as somehow aliens, haunted swords, an untrustworthy kitten and even a cross-dressing curse all come into the mix as well. Will our embattled butler fight his way through these epic complications? Or will his undoing come special de-livery? 
 
(Source: Sentai Filmworks)

It's never easy to be a gentleman's gentleman, but working for a girl who's not only not a gentleman but also a lightning rod for trouble (and not always particularly ladylike either) is a job that few butlers could handle. For Hayate Ayasaki, however, fighting off teenage heiress Nagi Sanzenin's would-be kidnappers is as much a part of butlering as serving the tea. Nor is that the only dangerous activity that Hayate's bound to be asked to perform during the course of the average day. Need to nurse everyone through an illness? Then that's part of Hayate's job description. Got an embarrassing video that has to be retrieved before it hits the internet or need help returning stolen money? Hayate's your manservant! However, as competent as Hayate may seem, there's one thing he's not particularly good at: noticing when pretty girls are attracted to him. Which is probably a good thing, as otherwise the silverware might never get polished! 
 
(Source: Sentai Filmworks)

It's no understatement to say that the stormy relationship between Nagi and her butler Hayate is often the result of the fact that they see things from entirely different social perspectives. However, when Nagi decides to bring Hayate, her maid Maria, and their friends to a secluded vacation retreat, our star-crossed couple soon find themselves seeing things from completely conflicting realities! In a bizarre turn of fate, Hayate finds himself in a world where his mistress is Maria, and Nagi no longer seems to exist! Meanwhile, Nagi is having her own problems, trapped in an amusement park of doom! What's going on and how does this relate to a mysterious silver-haired woman who seems to hold the key to everything? 
 
(Source: Sentai Filmworks)

The second season of Hayate no Gotoku!. 
 
Ever since he first met Nagi Sanzenin, Hayate Ayasaki's life has become increasingly more crazed and chaotic. Which is a bit of a problem, since, as the eccentric heiress' butler/personal bodyguard, he's theoretically supposed to be a stabilizing and protective influence. Unfortunately, Nagi and her friends attract trouble the way dropped lollipops attract dirt, and if Hayate has to take a couple of nasty licks along the way, that's just part of the job. The real sucker punch, though, is that Nagi's increasing attraction to Hayate himself is getting precariously close to transforming their professional relationship into something far less professional and much more like a relationship. Is Hayate up for the emotional perils of a round of "upstairs, downstairs"? Or will the purely physical dangers of life on Her Majesty's Domestic Service do him in first? 
 
(Source: Sentai Filmworks)

To encourage Nagi to swim and enjoy summer, Maria invites various friends to their Sanzenin family's private beach. While everyone is having fun, Nagi hesitates to wear swimsuits and come out because of her small breasts, and refuses to join...

Hardworking Hayate has a plan to pay back the yakuza—who are now the legal owners of his body parts: he’ll kidnap someone and ransom them for a mountain of money! But things get tricky when his would-be kidnappee—who as luck would have it is the daughter of a mind-bogglingly wealthy family—mistakes Hayate’s actions for a confession of love, and subsequently hires him to be her personal servant. At least his employment future is secure, or so he thinks…
 
(Source: Viz Media)

Collection of Hata Kenjiro's early works. 
1-5. Umi no Yuusha Lifesavers 
6. <a href="http://myanimelist.net/manga/37413/Hata_Kenjiro_Shoki_Sakuhinshuu:_Hayate_no_Gotoku!_no_Mae/moreinfo">Kamisama ni Rocket Punch!!</a> 
7. Hayate no Gotoku! Special (There is Life in Convenience Stores)