|“||Those who think they'll win are full of openings.||”|
Midorikawa is a short boy with messy chin-length brown hair and green eyes.
He has two uniforms. The first one, first seen during the Border Enlistment Arc, is an all-white Border uniform, similar to the C-rank uniform but with black stripes instead of orange ones. His uniform also has horizontal stripes on the collar and around the tips of his jacket's sleeves, and vertical black stripes on the front sides of his pants. He always wears his jacket unfastened, possibly as a nod to Jin, who wears his jacket in the same fashion. He also wears goggles around his neck, another possible reference to Jin. He also wears dark blue boots with white vertical stripes and gray soles. He wears this uniform again in the B-Rank Rank Battles Arc.
His second uniform, and his Squad's uniform, first seen in the Third Neighbor Attack Arc, consists of a black jacket with sleeves that reaches to his elbows with the upper halves being golden and striped. It has white stripes on the borders of the collar, zip fastener and bottom, and also from the collar until the sleeves and also golden stripes around the edges of the sleeves. On his left chest is the Kusakabe Squad emblem, and beneath it, the jacket has an interior pocket on each side, both with golden covers and silver buttons. Along with it, he wears black pants and gold-colored boots.
Yoneya has likened Midorikawa's personality to a "puppy dying to show off its talents". This was shown when he humiliated Osamu by defeating him effortlessly ten times in front of a large crowd, and when he became increasingly angry being defeated by Yūma time after time until finally recognizing Yūma's strength and calming down, although he was still defeated. However, in front of Jin, he acted very silly and energetic, because Jin saved Midorikawa in the past. He looks up to Jin and wants to join Tamakoma Branch. He has been shown to be able to think logically and strategically in a battle.
Midorikawa is very thankful for Jin for saving him, and is always trying to impress him and the other A-rank agents. He becomes very goofy and energetic around Jin. He also usually dresses similarly to Jin when not on duty.
Midorikawa and Yūma are friendly rivals. Like how Midorikawa defeated Osamu, Yūma defeated him, purposely losing at first to make Midorikawa overly confident. He is also one of the few people to refer to Yūma by his given name rather than by his surname.
Midorikawa was jealous of Osamu for being part of Tamakoma Branch, like Jin. He purposely defeated Osamu in front of a large crowd to humiliate him. He apologized to Osamu after being defeated by Yūma, but Osamu promptly forgave him. He now addresses Osamu as "senpai".
Their relationship is unknown, but although Kuroe seems antagonistic towards Midorikawa, they went to the same branch school in the mountains.
They seem to have a good relationship, and Midorikawa affectionately calls him "Yoneyan". They seem to frequently hang out, along with Izumi, and they visited Osamu together when he was hospitalized. Yoneya has also given Midorikawa advice on battles.
They seem to have a good relationship, and Midorikawa affectionately calls him "Izumin". They seem to frequently hang out, along with Yoneya, and they visited Osamu together when he was hospitalized.
- (To Lamvanein) "Those who think they'll win are full of openings." 
- (About Tetsuji Arafune) "Arafune was an attacker until 8 months ago. Besides, he had a good ranking. He still participates in rank battles with his Kogetsu. When he stopped being an attacker, everyone wondered why." 
- Shun (駿?) means "spirited horse". Midorikawa (緑川?) literally means "green river".
- Coincidentally, he has green eyes.
- His English voice actor, Nick Wolfhard, also voices Miyoshi.
- He has the habit of nicknaming others.
- He likes grilled meat, winning in rank battles, and Jin.