Gokudera was born in Italy and is 3/4 Italian and 1/4 (mother) Japanese. 
His blood type is B, is 168 cm tall, weighs 54kg and his hair is silver. His future dream 
is to become the Tsuna's right-hand man. He has an ability to play the piano. He dislikes 
people that are older than him, Bianchi and Lambo. Gokudera is also a chain smoker, but 
they remove this in the anime adaptation.

At school, Hayato is adored by many of the female classmates who view him as the 
"rebellious badboy." During Valentine's Day, a large group of females constantly followed 
him around trying to give him chocolate, although Hayato seemed to be more annoyed
 than flattered by this. Despite his image of a rebel, Hayato excels in his schoolwork and 
aces all his tests, much to the surprise of Tsuna. This is probably due to his rich 
upbringing, suggesting that he probably had a multitude of private tutors when he was 
young. He idolizes Tsuna greatly and considers himself to be Tsuna's right-hand man.

Due to a traumatic childhood experience, every time he sees the face of his older sister, 
Bianchi, he becomes sick, sometimes even falling unconscious. Oddly enough, he is 
immune to his sister when she happens to be wearing something that covers part of her 
face (i.e. glasses or goggles).

When he was younger, he was a talented pianist. However, he soon grew tired of 
playing after his 'trauma', and instead, decided to join the Mafia. Unfortunately, since 
he was considered to be a mere pianist, 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 dynamites, which caused Hayato's fascination with 
explosives, eventually choosing them as his main weapons.

In the future arc, more was revealed of 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 was a woman with whom he had an affair. 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, when 
she was killed after driving off a cliff on her way to see her son. It was probably not 
an accident, because, as Reborn says, "It slid off the road at an impossible location. 
It's been said that there weren't even tire marks. It was instant death." Suicide was 
considered, but she had been looking forward to that day and had even brought a 
present for the young Gokudera. Gokudera himself was unaware of what had happened 
until he was eight. He had overheard some servants gossiping and fled the mansion 
the day following.