Hosokawa was a poor delivery man who discovered the Mamodo boy in a freezer one day during his job, devouring frozen fish. From that day on, Reycom stayed by his side. One day, he was fired from his job, and began ranting at nobody in particular in his apartment. Reycom spoke up at that point, and showed him the powers of the book. Hosokawa saw the possibilities of the power he now held, and began using the power for his own desires, beginning by taking revenge on his ex-boss by attacking his car and sending him to the hospital, and then going on a spree of robbing banks and jewelry stores to get rich.
After an attempt to battle and gain Zatch as another weapon in his arsenal, the duo are defeated by the release of Zatch's second spell, Rashield. Reycom's book is ignited, and he fades away and returns to the Mamodo World as he tries in vain to slap out the flames.
Anime: In a slight adjustment in the anime, Hosokawa and Reycom are also the criminals who rob a jewelry store as opposed to generic criminals in the manga.
Manga: Hosokawa and Reycom are never even involved in the bank robbery in the manga, instead taking an interest in Zatch and Kiyo after seeing an article about the incident in the newspaper.
Reycom is then seen in the manga among the mamodo assisting Zatch with his final attack on Clear Note. In the mamodo world, Reycom could be partially seen as being in the same grade and class as Laila. In the end of the battle, Reycom is seen in a picture with all mamodo pictured by Zatch given to Kiyo.
Reycom is a humanoid child Mamodo with pale skin, spiky blue hair, gray eyes, and bags under his eyes, as well as the iconic vertical lines that many other Mamodo possess. His outfit consists of a dark blue shirt with white patches that give the blue a cross design on the front and back and a large silver snowflake in the center of the shirt, periwinkle pants that are several sizes too large, and consequently rolled and knotted at the bottoms of the legs, and gray and white tennis shoes. This outfit was shown to be in good condition on Reycom's arrival to the human world, but was shown to be worn and dirty by the time they met Zatch and Kiyo.
Reycom seems to have a laid-back personality; he rarely speaks or shows emotion, and goes with the flow of whatever his partner does, regardless of the wickedness or lack of sense in his actions. When asked by Kiyo why he put up with Hosokawa's abuse, he responded that he thrived on it, and used Hosokawa as much as Hosokawa used him, showing a malicious personality beneath his impassive exterior. He also showed some impatience when teaching Hosokawa how to read the book, and was very clearly horrified when his book caught fire.
Hosokawa is a middle-aged man with long brown hair with a widow's peak, high cheekbones, and wide shoulders. He was shown in various outfits during flashbacks, but is introduced wearing a black suit with white cuffs and gold buttons, a fuchsia collared shirt, a gold tie resembling a bearded lizard or cobra, and a pair of brown shoes with gold buckles. He also wore gold rings on five of his fingers.
It is implied that before he met Reycom, Hosokawa was a somewhat better man; he disliked his job working long hours for little pay, he thirsted for respect, and he was understandably furious when he was fired, but the initial concern with which he spoke to Reycom implied that he was a good enough person. This faded when he learned of Reycom's abilities, slowly and visibly losing any morals he had as he became drunk on the Mamodo's power. He's introduced as a greedy, selfish man who has no compassion for others, not even Reycom himself, whom he sees as merely a tool.
Reycom and Hosokawa as a team
Though they valued each others' abilities and personalities, Reycom and Hosokawa never saw each other as partners, only as means to an end. Hosokawa never thought of Reycom as more than a tool for his desires, and Reycom thrived on the abuse that Hosokawa put him through, as well as his rotten personality, claiming that it made him even stronger. The lack of any bond between them is evident in that Reycom never informed Hosokawa about his species or the Mamodo Battle, and that Hosokawa never cared enough to ask about what Reycom was.
That said, Hosokawa was skilled with using the spellbook's power, using spells quickly in succession and interchanging them strategically. Their growth rate was about average, having two spells at their disposal when they faced Zatch and Kiyo, and Reycom was shown to be competent enough with his power to not lose consciousness when his spells were cast.