Ayu is one of Heroes of the Sea Lifesavers characters. She is Natsumi's best friend along with Hijiri. Ayu is one of Hayate and Ayumu's friends who attends Shiomi.  She made an apperance in Hayate no Gotoku! Chapter 1 and Episode 37 in the flashback when Ayumu asked Hayate if he can take a photo sticker with her, but had no involvement in the main story.  (Source: Hayate no Gotoku! Wikia)

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)

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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)