Hayato means "quick man" while Myojin means "strange or unusual man".
Six years prior to the start of the series, Hayato met Ukyo while the both of them were training to become masters of their respective foodstuff (with Ukyo taking Okonomiyaki while Hayato took Takoyaki). The pair end up arguing which is better. Before the pair began their fight to decides which was better they each agreed that the loser should be forced to wear a mask for the rest of their life. Due to the larger surface area of Okonomiyaki, Ukyo easily won the fight, so true to his word Hayato wore the mask ever since.
Since losing the fight, Hayato describes his life as having become a living hell, with people staring at him in the mask as well as apparently countless girls rejecting him because of his mask. However, Hayato personally thinks the worst moment when he had to wear the mask was when a Mosquito flew into it, making his face itchy but being unable to scratch it.
After finding Ukyo again, Hayato sent his pet Patorasshu to continually ruin the Okonomiyaki which Ukyo was making just before it was given to the customers. Once this had occurred for a month, Ukyo finally notices Patorasshu and gives chase. This leads Ukyo, Akane and Ranma to Hayato, who tries to attack Ukyo only to be stopped by Ranma's intervention.
Hayato then shows himself to the trio, but Ukyo doesn't recognise him and demands he takes off his mask. This comment causes a very negative reaction from Hayato who soon flees afterwards. After fleeing, Hayato ends up outside the Tendo Dojo where, with his mask off, he curses Ukyo before quickly putting his mask back on when he senses someone behind him (in this case Ranma and Akane).
Curious about what the secret to Hayato's mask is, Ranma (who has no knowledge of why Hayato is wearing it as Ukyo herself has forgotten as well) tries multiple times to try to put Hayato in situations where he'd have to take his mask off, only to foiled at every turn. Eventually Ranma decides to take Hayato's mask off him when he's sleeping, but is again foiled by Hayato.
The two then begin fighting (meanwhile Ukyo remembers why Hayato's wearing the mask). While they fight, Ranma grabs Patorasshu and uses it to get Hayato's mask. Confused, Ranma tells Hayato that his face looks pretty ordinary, but this angers Hayato who uses Takoyaki batter to seal a mask onto Ranma's face.
Ukyo soon appears with Akane and Ukyo hits Hayato for what he's done to Ranma. After explaining about how wearing a mask has affected his life, Hayato puts back on his mask and says that he vowed not to remove it until he's defeated Ukyo. He and Ukyo then go off to building site for a rematch.
The pair begin fighting and at first seem evenly matched. However, Ukyo soon realises that with all the obstacles present at the building site, Hayato actually has the advantage since his small Takoyaki can fits through gaps which her Okonomiyaki can't. During a momentary break in the fighting, Hayato tells Ukyo that should she lose she'll have to wear a mask like he has, but Ukyo just tells him give up of the mask idea. The two of them then continue to fight each other through the night.
Early next morning, Ranma (who's managed to remove his mask) and Akane find Ukyo defeated by Hayato. Ukyo admits her defeat, but refuses to wear the mask. Hayato is fine with this as he's just glad to finally be able to remove his own without any worries. Unfortunately, in revenge before Hayato put back on his mask at the Tendo Dojo, Ranma had put Takoyaki batter in his mask. When discussing this at Okonomiyaki Ucchan's, Ukyo tells Hayato that he can put his face on the grill to get the mask off (the batter stops being adhesive when cooked).
Similar to Ukyo Kuonji, almost all of Hayato's attacks are based on his skill for cooking Takoyaki. As well as his attack technique, Hayato also seems to have very good agility, being able to jump/run away across rooftops with ease.
Barrage of Eight Hundred Blows: Described as a special technique, this is a rather simple attack where Hayato throws multiple Takoyaki balls at his opponent. The speed of which the Takoyaki balls are thrown is able to dent metal (namely Ukyo's Spatula) on impact.
Octopus Jar Drop: Another rather simple attack, Hayato uses an Octopus Pot to try and hit his opponent with great force.
Dance of the Restraining Dried-Fish Shavings: A distraction technique which Hayato uses to allow himself more time to escape from enemy techniques as well as temporarily slow down his opponent so he can strike them.
Takoyaki Spin: Using the large Skewer which he always carries, Hayato uses it to spin his opponents and thrown them off balance.
Octopus King's 'Big Ball Drop': Using his Skewer, Hayato is able to take a large Okonomiyaki and wrap it around himself before landing atop of his opponent. This seems to be Hayato's most powerful move, however, given how unlikely it is he'll face an opponent who can produce a large enough Okonomiyaki it may have been improvised during his fight with Ukyo.
With Ukyo: Upon first meeting Ukyo, Hayato didn't get on with her. Pretty much all this negative opinions of Ukyo stem solely from her preferring Okonomiyaki over Takoyaki. This was worsened when he lost their fight so agreed to wear a mask from that point on. By the time of him winning their rematch, however, he seems to have a less negative attitude towards Ukyo (even being willing to sit inside Okonomiyaki Ucchan's).
With Ranma and Akane: Hayato seems to get along with Ranma and Akane, despite their affiliation with Ukyo. He is very grateful of them for giving him somewhere to stay the night (although they were actually trying to remove his mask). When he did learn of what Ranma was trying, Hayato did become slightly more negative towards him, but seems to have forgiven him after his fight with Ukyo.
- Hayato has lots of similarities to Asuka Saginomiya, at least in terms of character design i.e. a rival to an already established character who they have a history with a fighting style that is the complete opposite to the style of their respective rival.