Other Characters

Yakuza:
The Yakuza are represented by three katana-wielding men in suits. One of them sometimes carries a chihuahua around. They are first seen taking Hayate away to harvest his organs until a mysterious hero called "Mask the Money" (actually Nagi in disguise) stops them and buys Hayate's debt off them. Later, they run into Hayate after he saved Isumi and told him that they actually like him for some reason. They then get into a fight with Isumi's bodyguards, which then evolves into a free-for-all after Hayate tries to leave without helping them.

The one wearing the yellow jacket on the right picture is called 'Kashiwagi'.
     

Mask the Money:
A mysterious hero called "Mask the Money", which is actually Nagi in disguise, surfaces because she did not want Hayate to know that she is the one to help him out right now. She manages to stop Yakuza and buys Hayate's debt off them. Despite her attempt to disguise herself, Hayate was able to know that it is Nagi behind the mask. He did tried not to hurt her feelings by pretending that he did not realize this at all.
     

Security 8801/9801:
Security robots that protect the Sanzen'in mansion. They fought against the Cockroach Man with the "jet stream attack" from Mobile Suit Gundam. They attack Saki and Wataru once under Nagi's orders as well, merely to prevent Hayate from knowing that Wataru is her fiancé. That backfired on Nagi literally with Hayate himself saving Wataru and Saki in the end. 		 
     
Santa Claus:
Santa Claus first appeared to Hayate in a dream when he was 8 years old telling him he had to work in order to live. Outside of Hayate's head, he appeared as a doctor after Hayate saves Nagi from a kidnapping. In the anime, Santa takes the roll of other minor characters such as a delivery man, a construction worker, a monster in a game, a waiter, Klaus' play school evaluator, a grocery store clerk, and a garbage man.
     
Nursing Robot Nine (介護ロボ9号):
Eight's successor. A giant robot with the head of a dog invented by the M.H.E. Electronics Corporation. It is equipped with nursing missiles, lasers, and a Kaigo Rudion.
     
Prototype Seven (プロトタイプセブン, Prototype Seven)

Prototype Seven is a machine created by Shiori Makimura for Gilbert Kent. It has Eight's version 8.2 operating system and data installed, the most violent version of Eight. Prototype Seven is supposedly controlled by the control chip, but it was left out by mistake because it was being built when Shiori was falling asleep. As a result, Gilbert loses control and it violently searches for Nagi in the sake of revenge. 		 
     
Taru Taru (タルタル, Taru Taru) - a stray kitten named by Wataru when he was little. Apparently, Wataru cares a lot about it and even tries to look for it under the rain, caring for it at the same time.
     
Cockroach Man (ゴキブリマン, Gokiburi man) - It appears crawling out of a well to kill those who watch the cursed videotape called 'The Wakka'. Maria is very much afraid of it since she is afraid of bugs. But in the end, she is able to protect Hayate from it before her legs gave up on her after it left. it is exorcised by Isumi Saginomiya eventually.
     
Makita and Kunieda (巻田・国枝): Seiyuu: Tooru Nara (Makita), Jun Oosuga (Kunieda)

Makita and Kunieda are Sakuya's personal butlers and always appear together. They don't appear unless they're told to do a task. Both butlers wear glasses and dark navy suits. Makita and Kunieda are very skillful. They can complete tasks instantly and perfectly, even amazing Hayate with their skill. In the anime, it is revealed that Makita plays the guitar and Kunieda likes to read books.

 
     
Mother of Hinagiku & Yukiji: Not much information revealed thus far except for the fact that she likes to drink tea?  
     
Strange Robot: It attacked Nagi at the first episode and ended up defeated by Hayate the next. He is seen being taken away after being dismembered apparently.
     
Nabeshin (Watanabe Shinichi): Appeared in upper part of Episode 32 as a comedic element. It seem that the director of the anime, Keiichiro Kawaguchi, invited Nabeshin to appear in his production. Nabeshin is fourth Kirika's mysterious dark butler coming to attack Hayate but he merely works part time. He has been without eat and sleep many days due to his busy schedule trying to produce and direct anime that he did not have the energy to fight Hayate. However, after being given food by him and Maria, he instill chaos upon Hayate with his family, and in the end, were chased out of the mansion by Yama
     
Da-man Mysterious Dark Butler: The second mysterious dark butler to appear at the end of Episode 30 to challenge Hayate to a Da-man Battle. Eventually lose to Hayate though.

(The first mysterious dark butler appear at the end of Episode 29 to challenge Hayate to a Yu-Gi-Oh Card Duel Battle. Eventually lose to Hayate though.)
     
Minicar Mysterious Dark Butler: The third mysterious dark butler to appear at the end of Episode 31 to try to beat Hayate in a minicar competition. Eventually lose to Hayate though.  
     
Tochigami: A deity that dwells in a property's ground appear in lower part of Episode 32 before Isumi and Sakuya to plead to them to help him chase out a phantom designated as Phantom KHV (Koi Herpesvirus) by Isumi. Isumi and Sakuya eventually help him out, managing to exorcise the phantom in the end. He loves synchronized swimming much to Sakuya's disgust.  
     
Phantom KHV (Koi Herpesvirus): The phantom that tries to eat the Tochigami in the lower part of Episode 32. He foguth fiercely against Isumi and Sakuya who tries to exorcise him, being inches from destroying Sakuya when Hayate appear to save her. It can transform into a giant and make clones of itself (At most three at one time). However, he is eventually gotten exorcise by Isumi and her immense spiritual power.

     
Itsuki/Shunji: In Episode 31, they appear to be lost kids roaming outside Nagi's mansion when Hayate fetch them in for a reason. Nagi is trying to prove to Sakuya that she can take care of children as well as she can by using them as the subjects. Nagi did her best to do that eventually without knowing what the two children were intending to do. It seems that they are here trying to steal some valuables and manages to lock their targets on a briefcase Sakuya said has valuable things inside. Sakuya already suspect them of something more than just being lost and she is right about that. They eventaully made it out of the mansion with Sakuya giving them the briefcase willingly, telling them to use the items inside and become successful comedians. 
     
King Turtle: While trying to help Hayate regain his memories in Episode 26, Nagi and Ayumu stumble upon an angry king turtle in Sanzen'in Lake, feeling rather unhappy that they step foot on his shell. It is about to deal with them when Hayate appear and manages to scare it away.
     
Isumi Saginomiya's Personal Butlers: These three butlers were always seen worrying about Isumi and authorize a search for her whenever she become missing again. They were so worried about Isumi that they even join the Bulter Battle Tournament in an attempt to win it so that Isumi will not need to go to school so often and get herself lost again. That is how serious her lacking sense of direction is. They were defeated by Himuro in the first round though as Isumi went missing again, this time finding herself in Paris, France instead of the tournament site.
     
Puppeteer Limited to Once (Seiyuu: Jun Fukuyama): This mysterious dark butler appear in episode 34 to carry out his own plan to defeat Hayate. He hypnotized Nagi first, telling her to lure Hayate and Hinagiku to the abandoned building in school and attack them with his own war machine. But in the end, he is still defeated but by himself as the war machine malfunctioned and self destructed. However, even after his defeat, Nagi did not wake up from his hypnosis. 
     
Dinosaur Like War Machine: Used by Puppeteer Limited to Once to fight against Hayate. However, it end up self destructing due to some malfunctions and took out its user instantly.  
     
Jormungandr: The pet of Kirika Kuzuha. It is actually the one responsible of giving Kirika and Shion powers to become a powerful sorceress and a man respectively. Kirika and Shion apparently found him guarding the butler treasure which is the ultimate butler uniform in the Amazon at the ruins of an ancient butler civilianization while searching for the legendary vanilla beans. Jormungandr had them mind controlled and bring him out of the ruins whose goal is to obtain freedom and not guard the butler treasure anymore. He wishes to obtain the power of the butler treasure thus making Hayate wear it and serve Kirika which indirectly served him. However, Nagi thwarted his plans when she tried to awake Hayate up from its mind binding spell and is defeated by the ultimate butler uniform in its final form. -
Cyborg Butler: Sent out to distract Hayate, the cyborg butler later defeated him when Hayate is stripped of his butler powers by Jormungandr. After taking a victory photograph with Kirika beside the fallen Hayate, he is ordered by Shion to finish him off. But Himegami intervened and manages to defeat the cyborg butler in time.
     
  Giant Robot: Used by Shion to fend off Nagi and the others from trying to make Hayate regain his senses and thwarting their plans. The giant robot fought Himegami almost to a stalemate, frying the SPs along the way. But eventually, it is defeated by Himegami who seems much more powerful than he looks.  
     
Mecha Butler 13: He took over Hayate's role as the combat butler of Nagi for a day as Hayate is given time to study on his own. He tries to learn more about human emotions especially jealousy but end up still finding it hard to understand. I do understand this: Nagi really likes Hayate. He end up attempting to destroy a incoming meteor colliding with the planet to save Nagi since he is a butler of Nagi. What is left of Mecha Butler 13 is left on the moon.
     
Piyo Piyo Terrorists: They are the ones who plant an explosive on Sakuya's ship, trying to kill themselves as well as everyone onboard as they want to get away from the debts they owe. They were easily subdued by the combat butlers at the scene but still manage to initiate the explosion and cause the ship to sink.