With is Dark's familiar, so he is probably the same age as Dark- 300 in the anime and 400 in the manga. He has been the family pet of the Niwa family, whose firstborn male sons are Dark's hosts, for many generations.
Eventually, Wiz became Daisuke Niwa's pet. The two play together and Wiz likes staying by Daisuke's side. One day, as seen in the episode Double Cooking, Wiz sneaked into Daisuke's bag and traveled with him to school. Daisuke discovered this after he arrived at school so it was too late to take Wiz back home. Daisuke told Wiz to stay in the bag and keep quiet or else they would both get in trouble. However, Wiz left the bag anyways and went to Daisuke's home economics class. Daisuke is shocked and scared when he sees Wiz in the corner and spills the food he was preparing on his friends, getting him in trouble with his stern home economics teacher. Daisuke rushes over to Wiz and tucks him under his apron. While Daisuke eats his lunch, Wiz peeks out from the apron and eats along with him. The home economics teacher announces that Daisuke and Risa Harada have detention together the next day since they didn't do well in the class.
That night, Daisuke scolds Wiz for the trouble he got him into and warns him not to come to school in his bag again. As Daisuke is holding him, Wiz begins to grow brightly and transforms into Daisuke.
The next day, an apprehensive Daisuke checks his schoolbag but Wiz is not there. then, as he reaches into his desk, he finds Wiz. Daisuke has detention that day but he needs to go on a thieving mission as Dark and doesn't have enough time to finish his detention. Then, he remembers that Wiz can transform into him, so he takes Wiz outside and tries to teach him how to speak like a human but to no avail. Wiz keeps pronouncing Daisuke's name as "Dai-suki", meaning "I like you." Finally Daisuke gives up and tells Wiz not to say anything at all.
When Wiz and Risa Harada's, who is actually Riku Harada in disguise, detention is done, the home economics teacher comments on how pretty the apron which Riku is wearing on like her. Wiz then says "Dai-suki" to a very shocked Riku.In the episode A Little Romance, Wiz wants to go shopping with Daisuke. Daisuke agrees, at Wiz’s insistence, as long as Wiz stays quiet, so Wiz jumps into their shopping bag. When they return with a bulging shopping bag, Daisuke finds Wiz in the bottom of the bag with something red smeared around his mouth and is concerned that they might have squashed him. Emiko assures Daisuke that Wiz is all right and is red from eating the strawberries in the bag. Daisuke sniffs Wiz and realizes she is right then finds out, upon checking the shopping bag, that Wiz finished all the strawberries.
The next day, in Daisuke’s class, his female classmates start talking about their pets. Since Daisuke is in the room, they ask him if he has a pet. He replies that yes, he has a rabbit and describes it as having floppy ears and being old. Riku Harada especially takes a marked interest in Wiz and wants to see him.
On the way home, Daisuke spots some unripe strawberries growing in pots and decides to buy a pot for Wiz. When Wiz sees the strawberries, he wants to have some right away, but Daisuke stops him and says that he has to wait till they are red to eat them and moves them to a windowsill.
The next day Daisuke goes to a place in his neighborhood where he has a view of the lake so he can paint the breathtaking scene. Upon reaching into his bag for his supplies, he finds Wiz inside. Dasiuke comments on how Wiz keeps wanting to travel outside then tells him that he must stay in the bag and hide when someone is coming. Wiz watches Daisuke sketch for a while then darts inside the bag when Riku Harada approaches. Riku asks Daisuke if he has spare time, then takes him to a pet store where a lop-eared female rabbit is on display in a cage by the window and asks if that rabbit looks like Wiz. Daisuke silently agrees that she looks like Wiz. As Riku and Daisuke examine the rabbit, Wiz peeks out from his bag, spots her, and is instantly smitten.
Riku sees him and remarks how cute he is and asks if she can hold him. Daisuke is alarmed and says that Wiz bites but Riku disagrees. Daisuke stuffs Wiz into his bag and hurries away (much to Riku’s chagrin). That night, Wiz gazes sadly out the window and Daisuke’s remark about the strawberries getting redder does not cheer him up. When Daiuke comments that Wiz does not have any energy, Wiz jumps off the windowsill and tugs at Daisuke’s bag, which Daiuke understands to mean that Wiz wants to go out again. He assures him that they will go tomorrow.
As Daiuke walks down a street with Wiz in his bag the next morning, Wiz jumps out and runs to the pet shop and tart hopping up and down to see inside the window. He goes inside and by the cage of the female lop-eared rabbit. Daisuke rushes inside the store after Wiz and stuffs him in his bag once more. The storekeeper approaches and Daisuke asks if the female rabbit bites, then quickly excuse him when the storekeeper sees his bag wriggling. Once outside, Daisuke scolds Wiz for running into the shop like that (because he could get arrested for shoplifting) and says that if he ever does that again, he will never take Wiz outside anymore.
That night, Wiz sits moodily by the window, and doesn’t eat his dinner or the strawberries. When Daisuke returns after eating, Wiz and one strawberry are gone and the window is open. Daisuke searches for him around town with his bike and finds Wiz by the pet store window with the strawberry in his mouth. Daisuke realizes Wiz wanted to give the strawberry to the lop-eared rabbit and tells him that the shop is closed for the night but they will come back tomorrow.
The next day, Wiz travels to the pet store by himself again but the rabbit has just been sold. Depressed, Wiz searches around town for her and even climbs up a windmill to look for her. However, he gets caught in a storm and begins losing his grip and slipping. Luckily, Daisuke and Riku, who have been searching for him, spot him and Daiuke is able to catch him before he falls. Wiz is happy to see them and glad to be out of the storm.
Daisuke takes him home and feeds him the now ripe strawberries, which he devours, seemingly having recovered from the sorrow of losing his love. Daisuke calls Riku to tell her what Wiz is doing and Riku says she thinks Wiz is weird and cute.
Daisuke Niwa: Wiz is Daisuke's pet. He and Daisuke are seen playing and spending time together on several occasions. Daisuke gets concerned when Wiz starts acting moody and depressed. When he discovers Wiz is in love with a rabbit, he tries to buy her but she is already sold. When Wiz disappers from home, Daisuke is really worried and searches all over town for him and saves him from plummeting to his death from a windmill.
Dark Mousy: Wiz is Dark’s familiar and will come to Dark at once if he calls him, no matter how far apart they may be. He can transform into Dark’s black wings, which greatly helps Dark on his thieving missions. Wiz can also transform into Dark himself. Though Dark always addressed Wiz kindly when he talks to him, Daisuke thinks that Dark does always understand how Wiz feels and that he, Daisuke, cares more for Wiz than Dark does.
Riku Harada: When Daisuke first talks about Wiz to her, Riku thinks Wiz seems cute and wants to see him. Later she takes Daisuke to a pet store where there he found a female lop-eared bunny which she thought resembled Daisuke’s description of Wiz. Wiz peeks out of Daisuke’s bag, where he is hiding and Riku spots him. She remarks how cute he is and asks if she could hold him but is turned down by Daisuke who lies that Wiz bites, which Riku doesn’t believe. She is the first to figure out that Wiz’s strange behavior is due to him having fallen in love with the female bunny and goes with Daisuke to purchase that rabbit. Upon discovering that bunny was sold, she refuses to buy another as that was the rabbit that Wiz likes. When Wiz is discovered to be missing she helps Daisuke search for him. After Wiz is rescued and Daisuke takes him back home, he calls her and she says she thinks Wiz is weird but cute.
Wiz can sense when Dark is calling him, no matter how much distance is between them. He can transform into Dark's black wings and is also capable of transforming into both Daisuke Niwa and Dark. He is only adapt at speaking in the manga and not in the anime. In both he is prone to saying "Kyu" rather than any words at all.
- In the anime adaptation, he is voiced by Megumi Toyoguchi. In the English dub, he is voiced by Mariela Ortiz.
- Wiz is much better at speaking English in the manga; this is a relief to Daisuke because he turns into Dark more often in the manga.