Iwasuke is a miniature dog of unknown breed. He has pointed ears and a thin tail with a thick clump of fur at the end. Although his fur is primarily light-colored, he has a darker portion of spiky fur running from the top of his head to his back, resembling a horse mane.
Iwasuke is docile and easily forms an attachment to Tsurugi. He primarily roamed around the area of the Wall Eyes near the springs and the site of the Higashikata House before living with the Higashikata Family in their home.
Intangibility: Iwasuke is capable of phasing through walls.
Yasuho Hirose initially sees the dog walking around near the Wall Eyes and Lover's Cape, in the spot where she first met Josuke. When she later leaves the Higashikata House's underground storeroom, she sees Iwasuke suspiciously walking around their property.
Tsurugi tells Norisuke and Josuke that he also saw Iwasuke near the Wall Eyes. Iwasuke turned all hard like a rock and looked crumpled, causing Tsurugi to assume he was dead. Yotsuyu Yagiyama then healed the dog by feeding him a Locacaca fruit and he suddenly got up and started walking again.
Wanting to learn the secret behind what healed Iwasuke, a trap with lots of dog food is laid out for him by Norisuke and Tsurugi. However, Iwasuke ignores it and doesn't appear. Later when Norisuke, Tsurugi, and Josuke are in the underground storeroom, Iwasuke mysteriously phases through the wall and enters the room. He jumps onto the bed to eat a piece of the Locacaca left behind which Yotsuyu was carrying. Josuke notices and yells at the two to grab him. Iwasuke doesn't run away and instead wags his tail while being pet by Tsurugi and Norisuke. The Locacaca drops out of his mouth and he starts eating Josuke's sesame honey dumplings. While the trio investigate the fruit, Iwasuke lies down and prepares to sleep. Norisuke asks what they should do with him. Tsurugi feels bad for him since he probably lost his home in the earthquake and declares that he'll keep him, naming him Iwasuke. Josuke and Norisuke glare at Tsurugi because of the "suke" suffix.
Iwasuke joins the rest of the family for their family photo once Jobin Higashikata comes home. Outside, Iwasuke is bothered by Tsurugi covering his nostrils with two fingers. He tries to bite Tsurugi but fails since his owner moves his hand away in time.
Iwasuke and Tsurugi confront Jobin in the garage, wondering what he's doing there. The three are then suddenly attacked by Ozon Baby and Iwasuke yelps in pain. He tries to run out of the garage while Jobin yells at Tsurugi to stop him. Unfortunately, he is dealt with more pressure and blood bursts out of him. He slowly manages to crawl away into his dog house. Jobin comforts Tsurugi by saying Iwasuke most likely turned his body into stone inside the doghouse so he can withstand the pressure.
- JJL Chapter 33: Josuke! Go to the Higashikata Fruit Parlor
- JJL Chapter 74: Ozon Baby's Pressure, Part 2
- JJL Chapter 53: Vitamin C and Killer Queen, Part 4
- JJL Chapter 22: Morioh 1901
- JJL Chapter 24: Paper Moon Deception, Part 2
- JJL Chapter 30: King Nothing
- JJL Chapter 34: Every Day Is a Summer Vacation, Part 1
- JJL Chapter 72: North of the Higashikata House. The Orchard
- JJL Chapter 73: Ozon Baby's Pressure, Part 1
- JJL Chapter 76: Ozon Baby's Pressure, Part 4