As a child, Amane had suffered from a birth defect where his circulation and heart failed to function normally. During the time of Amane's and Tsukasa's childhood, the current medical system was unable to provide the necessary treatment. Tsukasa usually went out to collect any souvenirs from the garden, including toys, flowers, and a kitten he brought inside the house, until he heard the news that his older brother wouldn't live long for the next month. Thus, it led him to compromise on a wish that costed a heavy sacrifice. Amane miraculously got better on the day of November 25th, which was the day of the twins' birthday, before finding that Tsukasa had already disappeared.

Amane attended middle school at Kamome and had Tsuchigomori as his homeroom teacher. According to Tsuchigomori, Amane didn't have any friends and always came to school wounded ever since his first year at the school. Despite Tsuchigomori's questioning, Amane refused to reveal who the culprit injuring him was. Amane gave Tsuchigomori his "treasure", a moon rock that he believed was from space, and stated that he wanted to go far, but then decided to not go anywhere, hinting about his changed past of dying before adulthood.

Amane's future was written in the books. He was to become a science teacher at Kamome Academy as an adult, but his future changed and he ended up with the fate of killing his own twin brother, Tsukasa, with a knife. Hanako himself died due to unknown causes not long after, tragically becoming a ghost and the only known human to Tsuchigomori (at that time) to change their future.

After becoming a ghost, Amane Yugi became known as Hanako and took up the mantle of the seventh mystery. Far prior to meeting Nene and Kou, Hanako's abilities were sealed by the Minamoto brothers' grandmother, which is likely where the "seal" patch on his cheek came from. Presumably, this means Hanako's powers used to be even stronger than their current state. What event led to his powers being sealed is unknown.

Being the seventh school mystery and the leader of the Seven Mysteries, Hanako maintains the balance in the relationship between humans and supernaturals of the school, and is often seen helping others around and protecting the school. Hanako is cheerful, outgoing, and likes having fun. As a ghost, he is rather mischievous, then he enjoys teasing others and can be very playful and pranky. Despite his youthful persona, Yako and Tsuchigomori respect him and follow his orders as fellow school mysteries. He can become very serious at times, but at other times he appears very flippant. Hanako is also a bit sadistic at times, as shown when he happily threatened to turn Yako into fox udon (he often threatens others with his kitchen knife). Yashiro Nene describes him as someone who is difficult to understand.

Hanako's personality is similar to that of when he was human, except for the fact that he was very passionate and knowledgeable about astronomy and dreamed of being an astronaut. However, he no longer talks about the subject. Furthermore, when he was alive at least in the school, he seemed more closed and shy. He doesn't like talking about or being reminded of his past due to the negative associations.

When upset, Hanako tends to find isolated locations such as the rooftop. In the presence of others, he often smiles to mask negative emotions. Though he tends to smile at inappropriate times, seeming not caring about what is happening around him, his actions prove otherwise. He rarely talks about himself and it is hinted that this is because he fears of revealing his past to others. This self-isolation and bottling of his emotions leads to his tendency to make decisions without consulting others. Hanako rarely asks for advice or help when it comes to solving problems, and as such he can be rather callous. He often assumes he has the best answer to a problem and will go through with his solution even if it may come at a very high cost to either himself or the person he is attempting to help. He will even lie to further his goals, which makes him seem rather duplicitous at times.

Hanako has expressed a great deal of affection and concern for other individuals, especially his human companions, despite denying so. He is shown to deeply care about his friends and be especially kind to them, as seen when he constantly helps Yashiro Nene and sincerely apologized when he hurt her feelings. When Nene is tired, he cheers her up with a kiss, and on one occasion he searched all around the school to find the Mokke's hidden trinkets, which included Minamoto Kou's earring. He also opens up considerably with their company even though little is known about him, confessing that his favorite dessert is donuts, which surprised even Tsuchigomori. Despite his affection for his friends and general regard for human life, Hanako can also be apathetic towards those he does not value highly. He is willing to sacrifice or harm others if it would be beneficial to his close friends, particularly Nene, based solely on the fact that he likes her more than those he does not know.

Hanako wears the old Kamome Academy male uniform, a black gakuran with gold buttons, white-collar and red hems, a white, long-sleeved western shirt underneath, black shoes, and red socks. He also wears a black hat that has a white underside, a gold emblem, and red strings along the front seam to match his uniform. Hanako is often seen with and commands two hakujoudai—mysterious white fire-like orbs— with red and green circular cores respectively. On his left cheek, Hanako wears a white seal with a red-colored kanji for 封 written.

Occasionally, Hanako is seen wearing a long, flowing black cape that covers his shoulders and chest and matches his usual outfit. The cape has a gold and red collar with clasps and a red underside. His cloak also neutralizes spiritual lightning.

Hanako plays Hanafuda card games with the Mokkes. He also constantly helps Yashiro Nene and follows her around.