Kyosuke is a real estate agent, Aoi's brother-in-law and her older sister's husband. At some point, Kyosuke and his wife became responsible for the infamous cursed Yamaga family house where Toshio Yamaga, his family, and several other people had died and went to the house to examine it. Inside the house they felt the curse's presence, were haunted by the ghosts, heard footsteps, laughter, and Toshio's singing and were generally disturbed and scared by it. Due to the house's bad reputation, they also faced problems with selling it and couldn't find a buyer for a long time. Kyosuke soon realises that the place is cursed though his wife doesn't fully agree with him, refuses to believe it and wants to sell it regardless. Aoi overhears them talking about the house and the curse and decides to go there with her friends. After their visit to the house, the curse begins to pursue Aoi and her friends and kills them one by one. Eventually Kyosuke and his wife met Kayako and Takeo Saeki who finally agreed to buy the house. Kyosuke learns from Aoi that she's been at the house and concerned about it. His wife blames him for it, telling that it's because he talked about it at home in Aoi's presence. Soon after, Aoi is killed by Toshio in the bathroom and Kyosuke learns of her death from her sister. After Aoi's funeral, Kyosuke's wife still sells the house to Saeki couple even after all that happened and soon after the curse kills her too, but Kyosuke himself manages to survive and live for over 10 years more. Eventually, he met Naoto Miyakoshi, who investigated the curse, trying to save his friend, Yui, and came to him for help. Kyosuke warns him about the curse, tells him about Toshio's first death, and about Aoi's and his wife's fates. Later, Kyosuke learns about Yui's and Naoto's demise and decides to demolish the Saeki house in hopes that it will stop the curse. He locks up, demolishes and barres the Saeki house from being built ever again, but it doesn't help. A year later, Kyosuke learns that Toshio had moved to Reo's house and begins to understand that the curse isn't over. Yui's older sister, Mai, came to the place where the Saeki house was while investigating her death and looking for Toshio and was disappointed to see that there were no traces of the house left. Kyosuke came to this place and met her near an empty lot. He told her about the house and it's fate and warned her of the curse, but she told him that she must find Toshio Saeki regardless for Yui's sake and asked him for his new address. After a short hesitation he gave her Reo's address and she set off to her house. It is unknown what happened to him afterwards, as he was never seen again, but he most certainly was killed by the curse eventually before the Saeki house was restored.
Kyosuke tells Naoto about the curse.
Desperate Kyosuke in front of the Saeki house, determined to demolish it.