"Huhu... haha. My lynchpin will seal the monster he had dragged out. That ought to make my skill be considered having surpassed his..."
Shuichiro Ayatsuki (シュウイチロウ＝アヤツキ), also known as Father, was the father of Nine the Phantom, and Celica A. Mercury. He was an incredible scientist, responsible for having made Kushinada's Lynchpin, and an Origin of the Grimoire that absorbs the seithr around it.
He is only referred to as “Father" during XBlaze Lost: Memories.
As a young man, Shuichiro had light brown hair with a white fringe that he wore slicked back, and a small brown goatee. He had amber eyes that were always covered by his glasses. He was always seen wearing a white shirt with a purple tie, a gray suit jacket, and a mage's cloak on top. He also wore grey trousers and brown shoes.
As an older man in the peak of the Dark War, Shuichiro had put on weight, but his attire, for the most part, had not changed.  However, by the time he was found, the seithr poisoning had left him gaunt, and almost unrecognisable to even his own daughters.
Preceding the death of his wife, Shuichiro was affectionate to his family, going to great scientific lengths in order to save them from tragedy. He was a well-respected mage, scientist, and husband; he would always try to make time for his wife and daughter, even when working.
However, the death of his wife haunted Shuichiro, as he believed he could have saved her. This drove him to distance himself from Nine and Celica, and became obsessed with his scientific pursuits. At some point, he did try to mend his relationship with his eldest, but the damage was irreparable. Shuichiro became jealous, and almost obsessed with Relius Clover and Yuuki Terumi as they ploughed forward with trying to create a Kusanagi. Come the time of the Dark War, Shuichiro had become an empty shell of the man he once was, as he had gone to great lengths to create the ultimate device to finally prove he was smarter than Relius - at the cost of one of his daughters. Before he died, he had descended to maniacal laughter and gibberish, but this could be attributed to his seithr poisoning.
Celica and Nine's father. A famous researcher whose work centers around the merging of souls and objects. He is also the creator of Kushinada's Lynchpin -- a device able to stop the flow of seithr from the Boundary temporarily.
His contributions to the scientific community earns him several awards. To further his research, he leaves behind his two daughters and heads to Japan... Nontheless, the Black Beast's sudden appearance on Japan, and the nuclear attack that followed results in Shuichiro's disappearance. 
The father of the main protagonist and her little sister. He engulfs himself in magic research and is currently overseas. Once he focuses on something he is incapable of seeing the world around him. A true researcher. 
- In the Six Heroes route of BlazBlue: Chrono Phantasma, the scenes based on BlazBlue: Phase 0 where Shuichiro is found in the First District were altered so that he never appeared.
- BlazBlue: Phase 0, Character Concept Artwork
- BlazBlue: Central Fiction, Library Mode, Character #058
- XBlaze Lost: Memories, TIPS, #40