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Appearance and Personality
Fumiya has a pair of large pupils within his almond shaped eyes with a finely shaped set of red lips beneath a straight, narrow nose which makes him look adorable. As a result, he often has to cross-dress during missions, which irks him greatly. Although he is already a high school student, there is still no sign that he is physically unable to continue pretending to be a girl, having not gone through puberty yet.
Born in June 2080, Fumiya is described as a cheerful, very serious young boy. Sometimes, he has difficulties handling his sister Ayako. Fumiya is someone who is open-minded and is able to understand that Tatsuya is more than just a guardian. He also admires and respects Tatsuya, even overestimating him.
Relationship with the Shiba Siblings
They have a good relationship with Shiba siblings since their childhood. They even visit Shiba siblings' residence for casual talk session and exchanging information.
Childhood (Mentioned in Steeplechase Arc)
One of the reasons Fumiya adores Tatsuya is because he taught Ayako her Perfect Diffusion spell that established her name, Kuroba Ayako, among the Yotsuba Magicians. At the same time, this became one of the reasons for the Kuroba twins to overestimate him.
Unlike the other members of the Yotsuba, he views Tatsuya as someone worthy of his respect and admiration. He calls him "Tatsuya-niisama" and is happy to see him. He even dislikes that his father views Tatsuya as only a mere guardian, and not a member of the Yotsuba Family.
Double Seven Arc
He wanted to go in First High to be with the Shiba siblings, but was ordered to enter Fourth High, as Maya thought it could possibly endanger the secret of Miyuki and Tatsuya.
In order to establish the fact that the twins and the Shiba siblings were complete strangers, they introduced themselves publicly, calling him "Shiba-senpai" and asked for guidance for engineering in order to set up an excuse to meet later.
As one of the candidates to being the Yotsuba heir, Fumiya is both skilled and powerful. In the Nine Schools Competition of 2096, in the Monolith Code event, he single-handedly took down First High School's team in the rookie division, a team that was undefeated prior to its match against Fourth High School's team and a team that included Shippou Takuma who was able to fight both Saegusa Kasumi and Saegusa Izumi at the same time to a standstill.
Like Miyuki, as one of the members of the Yotsuba Family, he was born with an innate ability which has the trait of unique Outer-Systematic Magic.
Among the living members of the Yotsuba family, he is one of the two (Other one is Tsukuba Yuuka) who has the highest abilities in mental interference magic. Although their skills were still inferior to their parents' generation, in terms of talent and potential, these two competed for 1st, 2nd place among the whole family.
- Direct Pain (ダイレクト・ペイン)
- This is Fumiya's innate ability and as with all innate ability, it can be used at a high speed even without a CAD. With this ability, Fumiya can directly "imprint" pain into another person's mind. Fumiya is able to control the level of pain his opponent experiences and can slip this ability in with another magic to fool his opponent about the source of his or her pain.
- Phantom Blow (幻衝)
- A flashy but intangible attack that can incapacitate the opponent by causing concussive-like symptoms using a single Psion shock wave.