Mutsumi Saburo / Hojo
Saburo Mutsumi
First appearance Keroro Gunso Volume 2 Encounter 19: The 623 Incident!!
Keroro Gunso Episode 1–B
Voiced by Akira Ishida (Japanese)
Joel McDonald (Funimation)
Wordplay name 623 / 326
Age 14 (debut)
Gender Male
Species / Type Pekoponian
Occupation Student / radio host
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Saburo in his first appearance[in?]

Mutsumi Saburo (サブロー 睦実 Saburō Mutsumi) (also 623 326; Mutsumi Hojo (北城 睦実 Hōjō Mutsumi) in the manga) is a fictional character in the anime and manga series Keroro Gunso.

Mutsumi also appears frequently in Seven of Seven as the radio DJ "623". Mine Yoshizaki, the mangaka of Keroro Gunso, did character draft work on Seven of Seven - Mutsumi is one of several characters who cameo on the show.


Mutsumi is a high school student with an I.Q. of 350 and is Kururu's partner. Mustumi skips class a lot and is rumored at school to be a member of a gang called the "Men in Black", though that doesn't seem to affect Natsumi's high opinion of him. He turns out to be a loyal and gentle but solitary guy - if he's aware of Natsumi's crush, he hasn't shown it, though he does take pains to read out her postcards when she sends them in to his radio show. Mutsumi is excellent in sports, academics, poetry, art, and philosophy, which is why he has a hard time fitting in with his classmates, and he hosts a late-night radio program which Natsumi compulsively listens to. He is the least-active main character of the series, but plays a fairly signifact role as Kururu's partner/friend and Natsumi's crush. In the anime, Mutsumi's identity as Kururu's collaborator is at first a secret (though it's quite obvious), whereas in the manga it comes almost immediately to light.

Episode 112 of the anime depicts how Mutsumi and Kururu first met. Since then, because of the fact that they shared the same wavelength, they became occasional partners. Mutsumi's name comes from Japanese wordplay (Saburo means 326, and Mutsumi means 623). Saburo's wordplay name, 326, also first appears in episode 112 on the Reality Pen. Kururu gives him the Reality Pen, which makes any drawing on a flat surface real.

In the anime, his identity as 623 is only known as the radio host, and his identity is kept secret to the public, while he uses his identity as Saburo in public life. While the 623/Saburo connection is hinted at several times in the anime, it isn't until episode 163 that this is officially revealed.


During his introduction in the second volume, Mutsumi is shown as calm, cool, and mysterious. However, when he reveals Kururu to the platoon, he shifts to a happier personality. He accepts Tamama's ideas about Coke from the faucets with joy, saying that it was a great idea.


Keroro Platoon

Mutsumi is the least participent human who is aligned with the Keroro Platoon, and has made the least appearances. However, this does not mean he is lazy or weak, in fact, quite the contrary. He volunteers on plots that interest him and is a very good comrade when in serious battles. In his appearances, he gives a great deal of support with the help of his virtual reality pen, which can create unimaginably powerful weapons and fascinating objects if he puts his imagination into it and draws it on paper, and with a quick and cunning mind Mutsumi has, this is pretty much the perfect weapon for him. He also maintains good relationships with his comrades with his easygoing nature and is never seen to be completely enraged or angry.


Kururu is the first member of the Keroro platoon that Mutsumi has met, but their beginning isn't exactly much for a start of a companionship. Kururu and Mutsumi immediately engage in fight, which after a surprising turn of events, Mutsumi saves Kururu's life while he gives the boy his virtual reality pen in return(anime). Since they're both misunderstood geniuses, they are capable of getting along with each other, and Mutsumi seems to be the only one who is shown to care about Kururu as a true friend. Mutsumi helps Kururu and his comrades on broadcasting-based plots, since Mutsumi is the anonymous (at least in the anime) 623, a popular radio DJ whom Natsumi is a big fan of. In the episode 229, when Kururu is alone, he says that he "can not let [their] bonds fade" and blows the whole invasion budget just to help Mutsumi. This hints that Kururu cares about Mutsumi as a friend as well.


Natsumi has been hinted to have a crush on Saburo ever since the first episode of the anime, but played no further part in some later episodes but his anonymous (at least in the anime) alter-ego is introduced as Natsumi's favorite radio DJ. Then later, in episode 9, he is introduced as the human partner of Kururu, the most secretive and somewhat irritating and sly member of the Keroro Platoon. Ever since then, Natsumi and Saburo have had more closer encounters before, but almost all of them end up as Natsumi being very embarrassed. Saburo thinks of her as a friend but hasnt showed any other feelings yet, while Natsumi desperately wants to confess to him. They have a chance of getting married. Saburo has gotten embarassed when Natsumi does cute thing though. Soburo seems to have a crush on Natsumi.


  • Saburo appears the least out of all the main characters and coincidentally, gets the last line of the series.

In Seven of Seven


623 in Seven of Seven.

Mutsumi appears for the first time in episode 6 as the late-night radio host 623. From there onward, 623's voice is usually featured at least once per episode on Nana's radio, and often just before the ending credits as well, toting a poem written by the DJ. Mutsumi's poems were often seen in the early Keroro stories as well; in the manga, he is a self-titled philosopher with an easygoing nature. 623 met Nana when she came to his radio station, and he appears again in person later in the series.

The most notable difference between the Seven of Seven and Keroro Gunso versions of Mutsumi is the color of his hair; in the former, it is an electric blue, and in the latter, a silvery-grey. He seems to be voiced by the same actor in both shows, though in Seven of Seven his voice is credited as simply "623, by 623." In the English dub, he is voiced by Sebastian Arcelus.


Mutsumi literally means "sweet fruit".

See also

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