Kuroboshi III (黒星三世 Kuroboshi Sansei) is the grandson of Kuroboshi.
He's an humanoid black cat, having green eyes and an orange star-shaped symbol in his forehead just like his grandfather, wearing a brown kimono and green hakama.
In the 18th volume front cover and some colored chapter front pages of the manga, his star-shaped symbol in his forehead is blue, his kimono is black and his hakama is striped blue.
He seems like a very friendly cat on the surface, he affectionately likes to linger around girls, sit on their laps and pay them compliments. Despite his pleasing personality, Kuroboshi III hides a secret shame: he is terrified of ghosts. Because of his terror of the supernatural, he has developed a preternatural ability to detect the presence of nearby phantoms, even ones that are able to hide from Rinne and Sakura. Of course, he runs away in terror or goes berserk causing a mess, as soon as he suspects one is lurking nearby.
As Kuroboshi wishes to retire soon, he and Tamako both ask Rinne to take on the task of training the child to follow his footsteps as Tamako's black cat by contract, for Kuroboshi feels uneasy to have Tamako train him. Rinne and Rokumon both try to help him overcome his fear, but the young cat simply cannot get beyond it and eventually goes to live and be trained at Tamako's house. He hardly makes any progress.
When he broke many of Tamako’s belongings in her storehouse by panicking of the presence of ghosts there, he has been ignored shortly after by her and his grandfather for 5 days, which looked as if she no longer acknowledges him and even fired him. But it turns out that while he was hiding afraid of being scolded, he ate a red manjū from a package that was found in the storehouse since it was delivered to Tamako on the Respect for the Elderly day, which rendered him invisible for a whole week to her and his grandfather who ate a white manjū.
Once, he was tasked to get a charm that would supposedly heal his grandfather of a strained back at an abandoned temple full of ghosts, although it was a ruse set by Tamako in hope that he would struggle to overcome his phobia for his grandfather, but the operation was a total failure.
He eventually makes one fearless communication with the spirit of a female kitten, when he became afraid of being thrown away by Tamako due to his lack of progress, since her story about having been thrown away made him able to sympathize with her, although it didn’t do much change to his phobia.
He, Oboro and Suzu searched for a lion headed faucet that pours water from the Sanzu river which is dangerous as it would send anybody with a boundary stone directly to the Wheel of Reincarnation, and they failed to notice that it was right behind them stuck in a fountain when they met upon Rokumon who finds it. The 4 are last seen enjoying a picnic together.
- Transformation: he can transform into kitten form.
- Sensing Spirits: he has an uncanny ability to sense even the most well hidden specter.
He would scratch Rinne on his face, taking offense anytime he calls her "Granny". He would nevertheless seek his help all the time.
He is fond of Tamako. They get along well.
He is quite fond of Sakura.
They have a good relationship. He hopes to follow his grandfather's footsteps, although he can't form a contract with Tamako until he overcomes his phobia, meaning Kuroboshi can't retire yet, much to his dismay.
- “How dare you address the beautiful Tamako-sama as granny!” (美しい魂子さまにむかっておばあちゃんとは何事ですかーっ！) – Chapter 176, while scratching Rinne’s face
- “You are so pretty miss, are you a princess from somewhere!?” (美しいあなた様はどこぞのお姫様ですか！？) – Chapter 176, when he meets Sakura
- “Yes, I’m really really scared of spirits” (はい、私、幽霊がこわくてこわくてたまりません) - Chapter 176
- "THERE'S A SPIRIT." & "THERE ARE SPIRITS." (霊がいますっ。) – Whenever he senses one or many ghosts
- His introduction after Kuroboshi resurfaces, is the following chapter in the manga, as Kuroboshi declared wishing to retire after getting out of the closet. While in the anime, he appears in the following season.