|Family|| Masayoshi Nakashima (father)|
|Home town||Miyagi Prefecture|
|Team||Wakutani South High (former)|
|Position|| Captain (former) |
|Affiliation||Wakutani South High (former)|
|Image gallery (4)|
He is tall and has an average build. He has medium-length black hair and thick, short eyebrows with similar colored eyes. He is first seen wearing a black tracksuit but for the Karasuno match, he wore a light-colored one.
He has a fancy-free personality and likes to leave his brother, Takeru, to take care of his other siblings. His sister, Makoto, commented that he is susceptible to nostalgia and often brags about how he and Takeru make the strongest combo.
He was once the captain and setter of Wakutani South High, but the team Takeru leads now is stronger than Isamu's. He, along with Takeru and Makoto, would often watch volleyball matches together.
Spring High Preliminary ArcEdit
Holding two megaphone cones, he cheers on Takeru with most of his family at the end of the Wakutani South vs. Ōgishō match.
He appears once again to cheer Takeru on during the Karasuno High vs. Wakutani South match. In the middle of the third set when Takeru's spike keeps getting blocked by Karasuno, Isamu grows frustrated. He's about to say that he and Takeru formed a better combo when his sister cuts him off and completes it for him, noting that he brags about it too often. Isamu sadly comments that he has a cold-hearted sister.
After the match ends in Karasuno's victory, he somberly joins the rest of his family in applauding the Wakutani South players for their performance.
He once formed a combo with Takeru and appears to be close friends with his brother despite being complete opposites, as noted by Makoto. However, Isamu often leaves Takeru to take care of their younger siblings so he could have fun.
At home, along with Takeru, they would watch volleyball matches on TV together. Isamu often brags to Makoto about his achievements with Takeru, which annoys her.
- He and his family appear in Kiben Gakuha, Yotsuya Senpai no Kaidan (where his sister is one of the main characters).
- Nakashima (中島) - Island in a River
- Isamu (勇) - Courage