Every time he sees the face of his older sister, Bianchi, he becomes sick, sometimes even falling unconscious. Tsunacalls it "Bianchi-phobia." This is due to having to eat her Poison Cooking whenever he had a piano recital, as his playing became terrible and distorted whenever affected by the poison, and was hailed by audiences as "unique", "modern", and "abstract". Oddly enough, he is immune to his sister when she happens to be wearing something that covers part of her face. As a result of his childhood trauma, he abandoned the piano despite his great talent and instead decided to join the Mafia. Unfortunately, since he was considered to be a mere musician, no one wanted to accept him into their family; the fact that he was an oriental half-breed lessened his chances of finding a willing Mafia Family to take him in. To become stronger, he sought advice from Dr. Shamal, who, at the time, was working for his Family. Hayato seemed to have looked up to Shamal, to the point that Shamal believed Hayato to have copied his hairstyle, and even wanted to learn his assassination technique, the Trident Mosquito. Instead, Shamal taught him how to use sticks of dynamite, which sparked Hayato's fascination with explosives, eventually choosing them as his main Weapon. This choice of Weapon lead Gokudera to become known as a human explosive because he hides dynamite all over his body, giving him the nickname "Hurricane Bomb" or "Smoking Bomb" Hayato. In the Future Arc, more was revealed about Gokudera's past. He and Bianchi are actually half siblings, born by different mothers. Bianchi's mother was married to their father, but Gokudera's mother was a woman with whom he had an affair with. Gokudera's mother was a young, beautiful woman and a very talented pianist, whom their father fell in love with at first sight. Not long after, they became involved and the woman bore a child. However, in the Mafia, illegitimate children are not tolerated, and everyone was told that Gokudera Hayato was actually from the same mother as Bianchi. His real mother was allowed to see him three times a year until he was three and was the one who encouraged him to play the piano. Gokudera's mother was not allowed to reveal her identity him, so he thought she was just someone who visited a lot. She suddenly died after driving off a cliff on her way to see her son, with a present for him (the present being why suicide was eliminated as a possible cause of death). When Gokudera was eight, he discovered that the woman that frequently visited him was his mother from servants gossiping, who implied that this matter was arranged by his father; this led him to run away from home. According to Reborn, however, it was neither a suicide or a murder, but "It slid off the road at an impossible location. It's been said that there weren't even tire marks. It was instant death." Future Bianchi made the further claim that Gokudera's parents both loved each other deeply and could have married. Gokudera's mother was actually very sick, and for this reason refused to marry Gokudera's father, believing she would be a burden to him. Bianchi believes that the illness made his mother lose control of the car. Despite several letters being shown as proof, Gokudera refused to give credit to this version of events.