|Full Name||Saijou Leonhard|
|School||First High School|
|Ability Name|| Data Fortification |
Convergent Systematic Reinforcement
|Weapons & Equipments|
|Voiced By||Takuma Terashima (Anime)|
|Novel||Volume 1, Chapter 2|
|Manga||Volume 1, Chapter 3|
|Anime||Episode 1, Enrollment Chapter I|
Leo seems to have great respect for Tatsuya, whose engineering skills and intelligence far exceed his own. Leo greatly trusts him and is willing to help him out however he can. However, that does not stop him from questioning Tatsuya's character at times and slightly fearing him.
Tatsuya seems to trust Leo as well. Aside from acknowledging his ability with "Fortification" magic, he uses Leo to test out a new weapon during the "Nine Schools Competition" arc and chooses him as one of his partners during the Monolith Code competition.
During the Yokohama incident, he learns that Tatsuya is part of the military, a secret unit called 101 Independent Magic-Equipped Battalion.
In volume 17, Leo has the same way of being with the Shiba being that during the meeting they had everyone except Shizuku, Honoka, the Saegusa twins, Minami, Miyuki and Tatsuya said a Mikihiko that he was aware of the reputation of the Yotsuba but Tatsuya is his friend and had proven to be a good person in their own way
The two hold a fairly friendly relationship where although they would hang out and be able to have casual conversations, the two also seem to bicker a lot. They often quarrel over things, ideas and motives etc. Either way this were often referred to as a "lovers-quarrel". They deny this in any occasion.
This relationship later evolves momentarily into a "master-student" one, when Erika chose to teach Leo some of the Chiba family's secrets in order to improve his fighting ability.
It is shown that the other characters in the anime have considered the possibility of them being a couple.