Tooru appears to be a slim man on the shorter side, being just slightly taller than Yasuho. He has curly hair styled in an afro on his head, with two white swirls on either side. He has thick eyebrows which he constantly throws up to show cluelessness or general happiness (usually around Yasuho).
He wears a dark vest over a sweatshirt that ends halfway down his torso, leaving his lower abdomen exposed. On the right breast of the vest, there's a symbol for the letter "S" with a sun surrounding it. A similar yet smaller "S" can be located on the crotch area of his pants. On either shoulder of his sweatshirt are two teddy bears. His pants have a floral pattern on them, showing what appear to be grape vines and leaves.
Like many Rock Humans, Tooru has grown to develop antisocial tendencies as a result of the first 17 years of his life being defined by solitude. While he's able to conduct himself personably and often behaves in a casual, upbeat manner, Tooru's authentic personality has an incredible sense of ruthlessness to it. This is best demonstrated by his particularly dangerous misfortune-based stand ability, as well as his apparent apathy toward the suffering of Yasuho, who he had interacted on positive terms with just hours prior.
Tooru is extremely ambitious and knowledgeable in both technology and medicine. However, Tooru also has a history of feeling as though his youthful appearance serves as a road-block in his ability to live up to his full potential. Notably, he attempted to pitch an innovative new idea to a number of prominent tech companies only to be dismissed as a result of his age and presumed lack of experience. As he explained to Yasuho, this caused him a period of prolonged anxiety and frustration over the idea that his life was going by without any achievements to his name. Tooru's main project is the cultivation of the Locacaca and creation of medicine in order to secure wealth and power. With his Locacaca Organization, Tooru set up a profitable scheme by healing the wealthy with the Locacaca, created or had someone create the miracle medicine Locacaca6251 as the next step of his plan, and took an interest for the new Locacaca, musing about the riches and the power he could secure by exploiting the new fruit's Equivalent Exchange.
Tooru has a somewhat unusual affection with Yasuho. It is shown that he met her when she was a little girl and she unwittingly helped him find someone to impersonate. Tooru says he had some fun discussing with her and hoped to meet her again. At one point, he became her boyfriend, and cherishes the memories he's had with her. Upon his introduction, Tooru wished to rekindle his relationship with Yasuho. Having previously grown apart due to his aforementioned period of poor mental health, Tooru is not only friendly but also flirty with her. For instance, he doesn't hesitate to touch her in an intimate manner and isn't disturbed that Yasuho openly rejects his advances, being sure that she has feelings for him. He occasionally teases her too, openly reminding her of their experiences together. Tooru's affection results in his relative mercy towards Yasuho, as when she confronts him, Tooru takes the time to warn her about his powers and proposes that she walks away to stay safe.
- Main article: Wonder of U
Tooru is a Rock Human, as well as the user of the stand Wonder of U. Wonder of U is able to create illusions which can be sent after a specific target. It can disguise itself and take on the appearance of a human, allowing it to interact with non-stand users. It can also create projections of itself, which can travel quickly between locations by phasing into and appearing on transparent surfaces, such as windows or picture frames. Wonder of U's ability is automatic and can be activated on any person who has looked at its back in either an attempt to pursue it, or otherwise moves toward it.
While Wonder of U's ability is active, targets will experience various instances of conflict which seemingly play out in the most devastating way imaginable. These calamities often involve an affected person repeatedly colliding with objects in their environment, resulting in far greater injury than is possible under normal circumstances. The ability's trigger is sensitive, as Mitsuba simply questioning the presence of Satoru Akefu at the Higashikata House was enough to activate it. The range of the ability is unknown, but it appears to be extremely large, as Josuke and Mamezuku were affected despite being nowhere near Satoru Akefu's supposed whereabouts.
Tooru, like other Rock Humans, was abandoned by his mother as a newborn and left in the wilderness. He shortly after infiltrated a wasp nest to continue his physical development. Approximately 17 years later, he rapidly matured into his adult body, killing the wasp colony in the process. He then traveled to Morioh and entered society undetected. It is implied that he had a hand in killing Rai Mamezuku's father as Wonder of U's human form was briefly seen at Mamezuku's Father's funeral.
Roughly ten years before the events of JoJolion, Tooru meets a young Yasuho Hirose, then a little girl. Noticing how she used her Stand Paisley Park to search through her mother's phone, Tooru impresses her by scraping two rocks together to make a fire while assuaging her doubts about him. Tooru asks for a favor and tells her to help him find someone, stating that he doesn't know their name but that he knows they are an elderly with a medical license and that they live alone and are isolated from their family. Yasuho finds her a suitable person to impersonate, Satoru Akefu. Tooru gives Yasuho the rocks to impress the other children at Yasuho's summer camp and disappears into the trees, wishing to meet Yasuho again after she'll have forgotten about him.
It can be inferred that he began impersonating Satoru Akefu with his Stand Wonder of U after that.
Tooru and Yasuho were revealed to have dated in High School, although it is unknown why Tooru decided to attend the institution. He then became a part-time worker at TG University Hospital at an undisclosed date.
Tooru encounters Yasuho during her confrontation with Wu Tomoki at TG University Hospital. He teases Yasuho about their previous relationship, but otherwise, the two are on good terms, as he is shown following through his promise to relay her message through to Josuke.
Afterward, Tooru repeatedly crosses paths with her as Yasuho follows Josuke and Rai across the hospital. Each time, he flirts with Yasuho and tries to remind her of their time together. He ultimately calls Yasuho and leaves a message declaring his love for her and says he wants to get together again. When Josuke gets into trouble after being accused of murdering a patient who died near him, Tooru reassures Yasuho as he promises to testify in favor of Josuke.
Tooru later meets Yasuho by the doorsteps of her house. After a speech about Tooru's aspirations and relationship regrets, Tooru asks her again to get back together but Yasuho is distracted by her investigation. Tooru offers his help and shows Yasuho a photograph of Satoru Akefu. Having seen the doctor's face, as well as confirming a link between him and Mitsuba, Yasuho decides to go to the Higashikata House.
Tooru doesn't accompany Yasuho but instead eats fast food for lunch. Yasuho calls him and asks him for help since she's injured at the Higashikata estate. Tooru says that he'll call an ambulance but Yasuho refuses, saying that she has a way to heal herself. Interested, Tooru departs for the Higashikata estate. Once there, Tooru ignores Yasuho's suffering and simply observes the estate from the surrounding forest while listening to music. When Satoru realizes Josuke's plan of "inviting" the head doctor to come to him, Tooru shows great intrigue at the sudden development.
Joshu comes out of the house with the Locacaca plant in his hands and Tooru retreats into the forest to remain unseen. Observing Joshu and Yasuho, Tooru decides to let Yasuho eat the fruit to confirm its power. Plus, he doesn't feel threatened by her. While hiding, Tooru makes some noise, and unwittingly allows Yasuho to realize that he's her enemy.
Yasuho confidently claims that he is the user of the calamity-causing Stand and a rock human. She dwells on their strange past together such as their first meeting when a young Yasuho was out with her troop. Tooru tells Yasuho that he appreciates her and has fond memories with her, warning her about the danger of her seeing him, since it would activate a calamity, killing her instantly. He then goes on explaining how the Higashikatas are already under this affect, as well as Rai and Josuke who he claims will die soon as well. Yasuho takes Joshu's phone and begins scrolling through the contacts. Tooru again warns her, asking for outsider assistance would count as a pursuit and lead her to be the first to die. Yasuho continues with her action and Tooru states that Yasuho has changed the order of death, meaning that she will die through calamity soon.