|Family||Tatsumi's Father (son)|
|Physical and Vital Statistics|
|Manga||Mentioned in various chapters|
Tatsumi's Grandfather was the grandpa of Tatsumi and Kasumi. He died before the events of the history. He has two known sons, Tatsumi's father and Hisatora, but he probably had another child who fathered his unnamed grandson.
In the flashbacks, he is awalys seen wearing a kimono or yukata with a pair of getas (a traditional Japanese footwear). His hair was long and grey (once probably black), which he tied in a ponytail.
Not much is known about him, except for the facts that Tatsumi says about his grandfather in the chapters. According to Tatsumi, he was good at sports but had a lot of hobbies in a lot of areas and he didn't stay with anything for long because he got bored easily.
Every week he would take Tatsumi to fishing and to climb mountains. He loved festivals and castles, and he always explained to Tatsumi in it detail about the castles. He also built the bathroom in the house for Tatsumi. Tatsumi would spend a lot of time in his grandfather's house and after he died, he stayed to live in the house because it was close to his school.