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He has a large horizontal scar stretching from cheek to cheek, crossing the bridge of his nose. Ken uses his Channels by inputing different animal teeth cartridges over his own which modify his physiology to reflect that of the animal he chooses. Despite not having a cartrige in, he is always seen with sharp canines. When doing this, a small image with the face of the animal will appear on his cheek. He is almost always seen wearing a green Kokuyo Middle uniform but for his casual attire, he wears a gray-blue hooded jacket over a yellow shirt with brown pants.
He likes to tease and belittle others, but he himself is very eccentric and over-confident. This causes him to clash with the calm, grounded Chikusa. Occasionally, during speech his tongue will pop out. He often speaks out of turn and as a result, is punished by Mukuro. It is shown that he demonstrates great loyalty towards Mukuro and will listen to all his orders even if it would mean sacrificing his own life. He is known to show a somewhat softer side where Chrome is concerned. Though he acts very harshly towards her in person, he is constatnly worried about her well-being and happiness, as demonstrated when he went shopping specifically for things that "would make her happy". Whenever his concern for her is acknowledged (usually by Chikusa), he denies it almost instantly and tries to play it off.
He was born into the Estraneo Famiglia along with Chikusa and Mukuro. All three of them were being experimented on as "guinea pigs". However, he and Chikusa were later saved by Mukuro, who had annihilated the entire Estraneo Famiglia. Ever since that massacre, they have been Mukuro's loyal subordinates.
Ken is the first of Mukuro's gang seen targeting an unnamed character. Later, he tracks down Ryohei, who asks him to join his Boxing club. Ken accepts the proposition on the one condition that Ryohei beats him in a fight. It is implied that Ken defeated Ryohei because he is later seen in a hospital. It is at that time that Ken pulled 5 of Ryohei's teeth. (In the anime, he gave him a watch that read 5 o'clock.), showing him to be the fifth strongest Nami-Middle student.
Kokuyo Land Invasion
At Kokuyo Land, Ken throws dead dogs at Tsuna's group, presumably to move them closer to the Botanical Dome. When Takeshi falls through the roof, he jumps in after him. He is amazed at how ditzy Yamamoto is in thinking that the dogs were actually puppets. Ken begins their battle by charging Takeshi, and when his opponent evades, he uses his momentum to leap into the air, put in the Monkey Channel, and then do a spinning wall-jump back towards Takeshi, who brings his bat out to defend. Ken uses the jaws of his Channel to destroy the bat with little fanfare. His opponent is visibly angered, but first asks him how he managed to change his appearance. Ken equates putting a new disc into a video game console to him putting teeth into his mouth to change his Channel. He demonstrates by switching the Monkey Channel for the Kong Channel, and heaving Takeshi into the glass walls of their arena. Off-screen, he switches to the Wolf Channel and reveals that because of the dead dogs' blood of Takeshi, he can smell him, while he can't be seen. And Ken proceeds to launch a flurry of quick attacks, which Takeshi dodges, trying to protect his arm. Reborn kicks Tsuna down into the arena, and Ken changes targets to the much weaker person. However, Takeshi throws a rock to get him to refocus on him. Ken charges and sinks the teeth of the Cheetah Channel deep into Takeshi's arm. However, he fell for the trap, and with a swift sword-butt to the temple, was knocked out by Takeshi. He taunts Tsuna's group after Takeshi and Tsuna are helped out of the hole, revealing that he managed to instantaneously switch to the Opossum Channel to effectively play dead. Bianchi proceeds to drop a large rock on his head (manga only). Ken reappears when Hayato is winning against Chikusa. He takes advantage of the fact that Hayato was suffering from Shamal's Trident Mosquitoes' countereffect, and digs the claws of an unknown Channel deep into Hayato's chest, which was the debilitating blow that won them their fight. As he watches his and Chikusa's opponent stumble and fall down a flight of stairs, they dawdle and give him time to release Hibari. He is defeated off-screen and tossed out of the window.
Ken and Chikusa appear when Tsuna was told to buy drinks after he questioned who the Mist Guardian is. When he reached the shop, however, Tsuna immediately fainted when Ken surprised him from behind. After a short conversation with Reborn, he and Chikusa left as he saying that Tsuna's Mist Guardian is too good for him. He later appear again in the gym where Mist Ring Battle took place, escorting Chrome. After Mukuro defeated Mammon, he changed back to Chrome who was exhausted and fell asleep. Ken and Chikusa left without her, stating that she isn't Mukuro and has no intention to give her his concern when Tsuna questioned them.
He and Chikusa watched Hibari's fight under Mukuro's order. During Gola Mosca's rampage, they saved Chrome from the mines that buried within the ground that she accidently stepped on. This left them unguarded and trapped between Gola Mosca and rifle pointed at them. Fortunately, Tsuna arrived in time, protecting the three of them from both attacks.
He and Chikusa secretly followed Chrome to the last match, but was found out by the Cervello and was told to stay and watch outside the battlefield along with Reborn, Collonelo, Basil, and Shamal until the match ends.
Battle with Glo Xinia
Ken, along with Chikusa, makes a cameo appearance during Chrome's battle with Glo Xinia in a flashback. He was talking about their secret hiding hole and put gum in it, after which Chikusa commented that gum was not food. Ken, along with Mukuro and Chikusa, makes another appearance during Chrome's battle with Glo Xinia. All three of them appear as Real Illusions made from Chrome, with the help of her Vongola Mist Ring.
Ken appeared alongside Chikusa and M.M. after Fran freed Mukuro from the Vendicare Prison. When they all arrived in Japan, they engaged Zakuro in combat, where Ghost came out suddenly and absorbed Zakuro's Flames. Ken also watched the fight between Tsuna and Byakuran. After Tsuna defeated Byakuran, Ken was seen with Chikusa and Mukuro calling out to Chrome that it was almost time they went back to the past.
Tsuna called Chrome at Kokuyo Land for a meeting with the Simon Famiglia, but Ken hung up on them. Later, he was happy when he, Chrome, and Chikusa received a package with food from an unknown sender, who was actually revealed to be Julie Katou.
Searching for Flan, Ken, along with Mukuro, Chikusa, and M.M went to countryside in France called Jura in order to recruit Flan into their team. However, when Mukuro's furious that his hair being compared to pineapple and Belphegor started to attack Flan with his knifes, Flan running away. Ken tried to stop and convince Flan that they're his allies but Flan immediately mocked Ken's habit on saying "byon" with smiley face, assuming him as an idiot fairy and tell him not to touch him or else he would catch his stupidity.
1st Day of Representative Battle
Later, after Mukuro was requested by Verde to fight for him, he is seen in Namimori accompanying Mukuro on his "declaration of war" statement to Tsuna. He and M.M protests when Verde starts to mock Mukuro, calling him a runt.
2nd Day of Representative Battle
During the second day of the Representative Battle of the Rainbow, he, along with Mukuro, Chikusa, and Flan, fought against Team Reborn and Team Yuni. However, when Colonello fired his Maximum Rifle attack, his and Chikusa's wristwatches were destroyed, thus disqualifying them from the battle.
3rd Day of Representative Battle
During the third day of the Representative Battle of the Rainbow, Ken and Chikusa uses the remaining two spare wristwatches, allowing them to rejoin the battle and help Mukuro to fight the Vindice with Team Reborn who had formed a temporary alliance with their team. However, he, Chikusa, Yamamoto, and Gokudera were easily knocked out by the Vindice after their true form was revealed. After the third battle was over, he and Chikusa was taken back to Kokuyo Land along with Mukuro to treat their injuries.
4th Day of Representative BattleHe and the other Kokuyo Gang members along with people who Tsuna had talked to gathered at Tsuna's house to discuss plan to defeat Team Bermuda. After the battle was over, he, Chikusa, and M.M visits Mukuro, Chrome, and Flan, in hospital and he is seen lying on Mukuro's bed with Chikusa and Chrome beside him when Hibari destroys the wall of Mukuro's room.
Like two brothers, Ken and Chikusa constantly bicker. At one point, Ken even tries to pick a fight with him, though Chikusa simply ignores it. Ken mostly mocks him by calling him "four-eyed Kappa". Chikusa is mostly irritated due to Ken's noisiness, mocking attitude and idiocy, though he is patient about it. Chikusa also dislikes the fact Ken is too lazy to practice good hygiene and will always tell him to take a bath. Chikusa also often patronizes Ken about trying to hide his concern for for Chrome by pointing it out at any given oppotunity. Despite all this, both are good partners and childhood friends as Chikusa is the first person that Ken trusts, and both always work together whenever Mukuro or Chrome are involved.
Ken displays great loyalty and admiration towards Mukuro who had saved him and Chikusa during their childhood. Ever since, Ken has been one of Mukuro's trusted subordinates to the point he doesn't mind even if he's just being used. Aside from this, Ken sometimes secretly pulls small pranks on Mukuro, such as wearing Mukuro's jacket, eating his chocolate ice cream out of the fridge, or calling him a "pineapple head," all of which are forbidden. This usually results in him being punished by Mukuro's Six Paths of Reincarnation. Initially it seems that Mukuro treats Ken indifferently like he did to the other of his subordinates and stated that he was only a tool. However, in reality, Mukuro values both Ken and Chikusa and cares for their well-being as far as striking a deal with Iemitsu for their safety.
Ken always treats Chrome harshly and mocks her, calling her stupid or ugly girl. He tries hard to show others his "obvious" dislike towards her. Initially, Ken only considered Chrome Mukuro's vessel, but he grows to truly care for her. He's always blushing whenever she is mentioned and worries whenever she's in danger or acting unlike herself. He will often try to cheer her up by bringing her snacks. He is quite protective, getting angry at anyone he feels responsible for making her upset. In Hidden Bullet: mono.CHROME, it's strongly hinted that Ken has harboured feelings for her ever since their first meeting. Chrome regards Ken as her first important comrade along with Chikusa and holds him dearly despite his mockery, as she possibly knows that Ken actually cares for her.
Their relationship had never been shown, but Ken had mentioned him as one of his friends during their times in Estraneo Famiglia. And, judging from his reaction along with the other children when Tony was shot dead by one of their captors, Ken seems to care for him.
Appearances in other media
He appeared in the Hidden Bullet Novel series. He appeared as a minor character in the first novel Hidden Bullet: Mukuro's Illusion, when Mukuro took over Kokuyo Land. And, also in the second novel, chapter one, Hidden Bullet: 2X-Fiamma: mono.CHROME, which tells how he and Chikusa first met Chrome: he and Chikusa went to Japan as ordered by Mukuro to find "the other me" in their dreams. Due to Ken missed Mukuro so much, he started to imaginating a pile of pineapples on the market 'talking' to him with Mukuro's signature laugh, making Chikusa commented that he had gone crazy. Ken retorted this and after some arguments, he left Chikusa and then fell asleep at Namimori Park. When he awake, he's surprised when he realized that he slept on someone's lap, who turned out to be Chrome who's still Nagi at time. When his stomach growled because of hunger, Nagi fed him an apple, which he accepted and tearfully ate as it reminded him the time when Mukuro also gave him an apple on the night they were running away from the Estraneo lab.
In the Reborn! artbook Colore; it's revealed that he often secretly wears Mukuro's jacket uniform, eats his ham from his fridge, and eats his ice cream in his freezer, which are all supposed to be forbidden. Unfortunately for him, Mukuro already knows all of this and is ready to punish him.
In the Chrome Saw It! A Happy Day at Kokuyo Land! Drama CD as a side character in Chrome's flashbacks and when he and Chikusa went to pick Chrome up form Tsuna's house. Despite Tsuna's protests about the fact that Chrome was changing, Ken kept on yelling for her to come out. When he suddenly says 'the pineapple-head inside', Mukuro switches with Chrome and uses his First Realm on Ken.
Lastly, he appears in the eight Drama CD "Namimori Radio - ON AIR!", where he's hosting one of Vongola's radio corner called "Ken Ken Paw's Corner". During the air, he constantly compares Mukuro's hair with pineapple, causing him to be nearly had his hair cut by Mukuro and nearly beaten up by him with the fourth path until Ken says it was a joke. However, in the end he is eventually punished by Mukuro when Chikusa reveals that Ken only feeds Chrome with chocolate snacks, angering Mukuro who uses his fifth path against him, and Ken's cries was heard as Mukuro cut the radio connection, ending the corner.
Weapons and Abilities
- Channels: Ken utilizes his Channels by inputting sets of animal teeth cartridges over his own, which modify his physiology to reflect that of the animal.
- Sun Ring: In the Final Future Battle Arc, Ken is briefly shown wearing a Sun-attribute ring while battling Zakuro.
- Ken doesn't bathe daily and claims to only take a bath once a week or a month. He even stated once in Drama CD that he rather being punished by Mukuro than being forced to take one.
- His favorite snack is peppermint-flavored gum.
- His favorite animal is bird because he thinks it looks delicious.
- His hobby is touring candy shops, fighting, and playing video games.
- He and Chikusa apparently know where Tsuna lives by tracking Chrome's scent as they went to pick up Chrome when Tsuna brought her over to his house to dry and change her clothes since Lambo caused a bucket of water, meant for Ken, to spill over her.
- Shusei Kagari from Psycho-Pass bears resemblance to Ken, as both characters were designed by Akira Amano.
- Despite having his own bed at Kokuyo Land, Ken prefers to sleep on the floor because he thinks that the bed is too soft for him to stay still.
- In the manga, he has the Opossum Channel, but he didn't have this in anime. He also had a wild boar channel in the Drama CD which was used to track Chrome's scent when he and Chikusa were looking for her and Kangaroo Channel in Hidden Bullet Novel.
- He has a habit of ending his sentences with "-byon."
- Because of his fangs, he has a lisp and can't say "shut up" and "why" properly.
- In Hidden Bullet Novel: mono-Chrome, it's revealed that he was the one who cut Chrome's hair into pineapple shape like Mukuro.
- A running gag in the Drama CDs, he is always compared to a dog and Ken would always retort that he's not a dog just because his name literally means dog (unaware that it was his behavior that caused him to be compared like one). Ironically, in several occasions in the series, dog ears and tail appears from him as comical effect. Mukuro also once used a command "Kanna, Ken" to him, a command that usually use for dogs in Japanese.
- His Fandom Shorthand is 14.