Kyousuke is the leader of the Little Busters and is a year older than the other members. He often comes up with absurd ideas, but almost always, he follows up with a fun or reasonable explanation along with it. He may suffer from a lolita complex, though he denies it. He's respected as a guiding figure by all of his friends and especially a role model for Riki. He is the older brother of Rin.
He was the one that triggered the creation of the artificial world, with the aid of the others involved in the crash. He's trying to make Riki and Rin stronger so they can face the reality that awaits them together; as the potential sole survivors. While some memories are clouded and may reset each time, Kyousuke repeats an endless cycle of everyone's last school semester together before the crash until progress has been made for the two, and all the other members can "let go." At first it's an endless fulfillment of fun, games, and togetherness for all, but he eventually decides to act seriously. However, his methods prove too strong for Rin, which causes her to suffer from a mental breakdown after the loop in which her route takes place named Refrain.
During Refrain arc, it shows that he can travel between the real world and the artificial world.
In the original Visual Novel: He constantly travels to the real world in order to delay the explosion of the destroyed Bus. He attempts to crawl many times to the gasoline leak, but each time he switches worlds to check on Riki and back, he spawns back to where he started, laying on his back far from his destination. Ultimately, he realizes that by re-enacting his "state of death" he felt the first time at the incident, he can alter where he'll "remain." He finally accomplishes this by crawling to and then stabbing himself with a shattered window shard, while using his own body to cover the pipe that was leaking gasoline.
In the anime adaptation, he maintains his progress while crawling in the real world and the "reset point" had been removed.
In the "true ending" where Riki and Rin manage to save everyone in the crash, Kyousuke is the last member of the Little Busters to return to the school from the hospital.