Atsushi Sendo/Synopsis

History
In the original timeline, Akkun stabs Masataka Kiyomizu and is arrested. After his release, he becomes a no-name punk.

Toman Arc
Atsushi and his friends leave the train and decide to eat hamburgers. While sitting in the restaurant, Atsushi comments that he is surprised that Takemichi's cousin is the leader of Shibuya Third Middle School. Kazushi comments that if third years appear, they will drop Masaru's name, so no one would mess with them. Takemichi wonders what they mean, which surprises everyone, and Makoto reminds him they are going to fight the second years and hype themselves even more.

They reach the school, but are unable to find any second years. Takuya wonders if they are avoiding them and Kazushi guesses they heard they were coming and ran away. A moment later, third years led by Masataka Kiyomizu appear, stating they heard they are looking for the second years, but they are on a school trip right now. Kazushi drops Masaru's name, but that causes the delinquents to laugh as they reveal Masaru is their errand boy. Masataka's gang then proceeds and beats Takuya and his friends, and tell them that they are not soldiers in Tokyo Manji Gang. Beaten up, they head home, but on midway Takemichi leaves them to go visit Hinata.

The next day, after Takemichi loses in Masataka's fight club, Takuya approaches him and wonders how he lost against that opponent, but Takemichi just apologizes. They meet the rest of the gang and get into the bathroom. Atsushi reveals that there will be another fight club today and Takuya will participate. That surprises everyone as Takuya is fragile and not a good fighter, but can't do anything as its Masataka's orders. Atsushi would even take his place, but Masataka won't listen. Takuya states he will win and tells Takemichi to treat him so gyudon. The rest give their support to Takuya and leave for the fight club.

Before the fight starts, Takemichi challenges Masataka, who accepts. While Masataka beats Takemichi, Atsushi approaches the ring and takes out a knife, intending to stab Masataka, however, he then realizes the crowd had stopped supporting Masataka as even though Takemichi is beaten badly, he keeps standing up. Atsushi puts away the knife and tells Takemichi to give up as he had shown them how tough he is, but Takemichi refuses stating that he has a reason and can't give up. Manjiro Sano and Ken Ryuguji appear and break up the fight club, beating Masataka. Later, Atsushi tells Takemichi that he planned on stabbing Masataka, otherwise they would have stayed slaves forever, but thanks to Takemichi, they are no longer slaves.

Years later, Atsushi became a member of the upper echelon at Toman and is given a hostess bar to run. Wanting to meet Manjiro and learning that Atsushi is in the upper echelon, Takemichi contacts Atsushi and he agrees to meet. Naoto goes with Takemichi, but wishing to talk in private, Atsushi takes Takemichi on the rooftop. He reveals that he knows Naoto is with the police and is Hinata's little brother. Atsushi also reveals he was the one that pushed him into the train tracks and he should have died, but Naoto somehow knew that was going to happen and saved him. Atsushi wonders if Takemichi can go back in the past and asked Naoto for help. Atsushi believes that's insane, but there is no other explanation. Takemichi refuses to believe that Atsushi would try to kill him, as he is his friend. Atsushi reveals that he is Tetta Kisaki's soldier and everyone in Toman obeys him, as they haven't seen Manjiro in years. Atsushi reveals that Manjiro changed after Ken Ryuguji died and asks Takemichi to go back in the past and save him, save everyone. After that Atsushi jumps from the rooftop and dies, causing Takemichi to start crying.

Moebius Arc
After Toman gets in conflict with Moebius and Takemichi spends sometime in the hospital, Kazushi and the rest visit him at home. They are surprised to see Ken coming in too an as Manjiro also shows up, Manjiro and Ken ends up fighting.

On August 3rd, during the festival, Atsushi receives a call from Hinata, who informs him the situation with Ken. Atsushi then gathers Makoto, Takuya and Kazushi and head towards the festival. They manage to come in time and stop Masataka's gang from attacking Takemichi and Ken. They get easily beaten up, but inspired by Takemichi challenging Masataka to a fight and not giving up, they refuses to give up and continue standing up against Masataka's gang until the ambulance arrives. As the ambulance take Ken to the hospital, he and the rest wait until the operations is over and celebrates with everyone when they hear Ken will live.

Since Ken lived and Tetta didn't become number two in Toman, Atsushi didn't work under him and didn't kill himself. When Takemichi returned to the present, Atsushi invites him to a salon. Takemichi wonders if he is a hairstylist now and Atsushi reminds him he is just an assistant. However, he called him here today as from next month, they will be allowing him to cut hair and he wishes Takemichi to be his first customer as they promised. Takemichi gets happy and starts crying, making Atsushi comment that he is a crybaby as usual.

Takemichi gets a phone call from Naoto Tachibana and goes with him to see Hinata Tachibana. Eventually Takemichi and Hinata are alone in the park and Hinata returns to the car, while Takemichi goes to the bathroom. Following orders by Kisaki, Atsushi rams into their car. As Takemichi shows up, Atsushi is surprised that Takemichi isn't in the car, but comments that he is Kisaki's soldier and is afraid of him. As he asks Takemichi to save everyone, his car explodes and kills him.