Mei's Grandfather is the father of Shou Aihara and the chairman of Aihara Academy.

He is a ruthless and unforgiving man. He does not tolerate any form of insubordination and will not hesitate to strike a punishment wherever he sees fit. He has a cold and calculating appearance, and never smiles. As the chairman of Aihara Academy, he deems it necessary to discipline the school as much as possible to uphold their high status image. He is seen to have a similar outlook as Mitsuko, the former school president who ran the school on a policy of fear.

Despite his unnerving appearance however, he does believe in second chances. He forgave Yuzu for her unruly behavior at the school gate when she called him "grandfather," as well as her outburst in their assembly. However he expelled her when he saw her half stripped on Mei's bed with her. However he did later allow her to re attend the school due to her phoning an ambulance for him.

Although he has a strictly business attitude, he is shown not to be above forgiving others.

(Source: Citrus Wiki)