He has a distinctive golden, spiky hair and is mostly seen wearing a sun glass on his forehead with a bulked up and muscled body. Fuutarou five years ago also shared similar facial traits to Isanari.
Isanari has a wild character. Fuutarou five years younger is said to share the same personality as his father, notably both were bad at studying.
Isanari and Maruo had a history of rivalry during school days, stemming from their differences. While Maruo was an exemplary student, Isanari was rebellious.
It was through Isanari's connection with Maruo that his son, Fuutarou, became a tutor for the Nakano quintuplets.
Isanari and the quintuplets' mother, Rena, knew each other during school days. She was his senior, or senpai (先輩?), as Isanari addressed her.
- "This is once in a lifetime event, don't you think that you could still make it?"