In flashbacks he appears as a young man in a formal suit. His appearance is virtually identical to his twin brother, Futaba, aside from perhaps the sweep of his hair (Kazuha's sweeps to his left).
In the present, he is an elderly man who is wheelchair-bound. He wears a coat and pants with a scarf around his neck. A blanket covers his legs.
Kazuha and his brother, Futaba, were born as twins to unknown parents. As adults, the two ran a business together which performed well in the post-war economy. Futaba formed a relationship with a foreign woman and Kazuha was not happy with Futaba's wish to be with her.
During a celebration event for the business, Futaba announced his desire to be with his lover to them and departed with her to Kazuha's pleas.  Futaba would later perish while eloping. Kazuha claimed Futaba's body as his own and has since then gone on living in Futaba's identity. Over the years, he grew bitter and loathed the woman his brother loved.  He received Suiseiseki and Souseiseki after answering the question to wind in a dream. He wound up Souseiseki first and quickly made a contract with her after the doll declined his request to kill his soul tree, but agreed to kill the soul tree of the woman his brother loved. As they would be unable to do this without her, he wound up Suiseiseki and demanded that she work for him. Suiseiseki refused, sending her into conflict with Souseiseki and Kazuha. The next night, Suiseiseki switched clothes with Souseiseki and attempted to trick Kazuha into breaking the contract between him and Souseiseki. When the real Souseiseki came in he realized Suiseiseki's trick and spanked her. Souseiseki, while also upset, defused the situation by telling Kazuha that Suiseiseki would be leaving the mansion in the morning. That morning he ordered his maid, Hozumi, to beat Suiseiseki if she saw her.  Kazuha orders Souseiseki to retrieve Suiseiseki but would later state that taking the watering can away from her would also be acceptable. 
Jun Sakurada, Shinku, Suiseiseki, and Hinaichigo enter the Rose Mansion to confront Kazuha and Souseiseki. During this conflict, Kazuha traps them all in a field and while watching Suiseiseki and Souseiseki fight by Futaba's lover's soul tree, he comes to realize his delusions about his past. He admits he was wrong and that he feels trapped by this person he's become. Souseiseki also has a similar realization and, to make up for her own actions, grants Kazuha's wish to be freed from his delusions, shattering that part of his soul.  This kills Souseiseki in the process, her last words to him and Suiseiseki being that they both strong enough to go on. He reacts in surprise as Suigintou steals Souseiseki's Rosa Mystica.
Kazuha expresses his grief over losing Souseiseki saying that he will cherish her for freeing him.  Her case and body is kept with him. Suiseiseki would later pay him a visit to see Souseiseki and finds out that he's been having tea with her inactive body. Suiseiseki scolds him for this, saying that her body should stay in her case, but stays to have tea with him because he's been lonely. On a later visit, Suiseiseki shows him Souseiseki's hat, explaining that she found it while in the N-Field. The two check Souseiseki's case and discover her body missing.
It is later revealed that Kazuha is in hospital in a deep sleep having been caught in Kirakishou's seedbed.  Suigintou would later free him from this, annoyed as he insists that she's actually Souseiseki. 
In the final chapter, now awake in the real world again, he is seen waiting at his tea table for Suiseiseki and Souseiseki to show up. 
References and Citations
Yamamoto • Mr. Umeoka • Futaba Yuibishi • Alice (Rozen Maiden (2008))
Kazuki Shibasaki • Matsu Shibasaki • Yuna Kuwata • Hitomi Sakamoto • Enju
Ageha • Yamaguchi • Megu's Father • Megu's Nurse • James • Head Manager