The culprit is Miyuki Hyuga, while Hideomi truly committed suicide. The motive is that Hideomi and Mitsuaki started the fire that killed Miyuki's parents. Miyuki learned the truth after finding Hideomi dead. There had been more to his suicide note which reveal his and Mitsuaki's role in the fire. Miyuki then decided to avenge her parents by killing Mitsuaki and framed Hideomi.
People
Kuranosuke Take
72 years old
Butler to the Nagato family
Dosan Nagato
60 years old
Chairman of Nagato Financial group
Miyuki Hyuga
26 years old
Personal secretary to the Chairman
Nobuko Nagato
39 years old
Dosan's eldest daughter
Yasue Nagato
32 years old
Dosan's second daughter
Hideomi Nagato
Victim (poison)
36 years old
Dosan's eldest son
Novelist
Mitsuaki Nagato
Victim (impaled)
36 years old
Yasue's husband; took Nagato name
President of Nagato Construction
Major events
The reason Conan couldn't let Miyuki Hyoga commit suicide is because of what happened during the Moonlight Sonata Murder Case.
The potter Kikuemon invites Kogoro, Ran, and Conan to his home, as he greatly admires Kogoro. He lets Kogoro choose one of his pieces as a gift. Afterward, he shows his guests the large kiln in the garden. Suddenly, they hear Kikuemon's daughter-in-law, Masuko Tsuchiya, screaming loudly in the garden shed. Kikuemon's latest artwork has slipped off a ladder and shattered on the ground. Next to the ladder, Conan finds a marble.
At dinner, Masuko gets drunk and is put to bed by Yoshihiko Arita. The next morning, she is no longer in her bed and doesn't answer her cell phone. Suddenly, those present hear something break in the garden shed and find Masuko hanged inside.
