|Novel(s):||BlazBlue: Bloodedge Experience — Part 1|
A man in his mid-40's with square rimmed glasses, Tadayuki Isa is a faculty member of the Shin Kawahama First High School. His subject includes teaching about geology, mineralogy, petrology, geophysics, geochemistry and seismology. He appeared to be suffering from some sort of illness where he makes insect-like verbal tics. At some point, Tadayuki had filmed Kana Kirishima walking into an adult store; he used the tape as blackmail to force her into perverse sexual acts.
Bloodedge Experience — Part 1
Tadayuki briefly appears during Chapter 1: Contact when he teaches Earth Science to Naoto Kurogane, Haruka Hayami and Shinnosuke Fukuda. During class, he seemed to be acting particularly strange, and began screaming at Naoto when the latter asked if he was alright; instead of going to further berate Naoto, Tadayuki began to make strange insect-like noises.
During the lesson, Naoto scoffed at Tadayuki's ridiculously low life-force value (at the time, only a mere 925), commenting that even patients who have been hospitalized have higher values than him. After school, Naoto attempted to find the teacher, but he had disappeared before Naoto could do so.
Some time after school, Tadayuki suddenly directed Kana to deliver sexual toys to him, trying to force her to bring Haruka to his domain since he was becoming bored of Kana. He then apologized and began to strip Kana out of her coat; several insect noises emanating from his throat, he told her that they will begin.
Days later, Tadayuki stayed behind at school when Haruka had work to do for the school counsel. He walked into the school counsel room and began to converse with the young girl, locking the door to the room and calling her work ethic admirable; he then set up a camera on a nearby table and began to take off his clothes, revealing that he wore a leather outfit underneath. He then took out a leather whip from his bag and handed it to Haruka, begging her to hit him with it while calling him a 'pig', shocking the young girl even more. Digging deeper into his bag, Tadayuki pulled out a black piece of clothing and began to rip Haruka's clothes off, screaming at her to wear it. Fortunately for the young girl, Naoto rushed in and punched his teacher square into his face.
The teacher rose up off the ground, with more beetle-like sounds screeching from his mouth as two insect-like legs grew from his back. Tadayuki attacked, but to no avail due to Naoto's regeneration ability, and instead switched targets to the nearby Raquel Alucard, only to have Naoto jump between the blow, with Tadayuki's newly found legs piercing his stomach and arms. Naoto punched out the arms and Raquel's Drive, Tempest, sent the teacher spiraling across the room. Arising once more, Tadayuki attacked Naoto, but his attack was suddenly deflected by the student's Bloodedge; the blade then cut away at the teacher's legs and the student continuously punched the sick man until consciousness slipped away from him.
The Mitsurugi Agency then arrived and they carried Tadayuki away to save him from the insect that had infected him. The bug was safely extracted and the teacher took a temporary retirement in order to recuperate.