From Anime News Network:

yohmeiFuji TV has announced on Saturday that 74-year-old voice actor Takeshi Aono remains in a hospital due to a stroke he suffered after surgery for aortic aneurysm. As a result, 55-year-old Bin Shimada will substitute for Aono as Tomozou Sakura – the grandfather of the title character in the Chibi Maruko-chan television anime series – starting with the episode that airs on Sunday.

According to Fuji TV, Aono was admitted to a hospital for surgery at the end of May, and was diagnosed with the cerebral infarction after the operation. While Aono’s current condition is improving, the prospects for his return to work are uncertain.

He voiced Yohmei Asakura, Yoh’s grandfather on the Shaman King Anime. Shaman King Nation wishes for him to have a speedy recovery. You can read more of the story at ANN.