Iwao Yamakawa is an elderly man, the maternal grandfather of Kobo Tabata. He shares a home with his wife, Mine Yamakawa, their daughter Sanae Tabata, her husband Kouji Tabata, and their grandson Kobo, alongside the family pets—a dog named Bochi and a cat named Mii.

As a member of this multi-generational household, Iwao participates in daily domestic tasks, tending to both the family members and their animals. His appearance features balding black hair and facial hair, fitting an elderly character design. He engages in typical family interactions and routines, often contributing his generational perspective to minor household situations.