Johann is a young craftsman from the city of Ehrenfest who plays a crucial supporting role in the world of printing. He is a metalsmith by trade, initially working as an apprentice in a workshop before eventually striking out on his own. His exceptional skill lies in precision metalworking, a talent that distinguishes him from other artisans in his field.

Johann’s personality is a study in contrasts. On one hand, he is a devoted and meticulous perfectionist, taking immense care with every detail of his work. This dedication to his craft, however, comes with a deeply pessimistic and self-doubting nature. He has a tendency to bombard customers with so many detailed questions about their orders that he often discourages potential clients and struggled to secure a regular patron because of this finicky approach. This lack of self-confidence is a core part of his character, making him unaware of the true value of his own extraordinary abilities.

His life and career are transformed when he encounters Myne, the protagonist, who later becomes known as Rozemyne. Johann first meets Myne when she commissions a diptych and stylus, and he is immediately struck by her willingness to answer his endless stream of questions. Recognizing his skill, Myne later gives him the daunting task of forging an entire set of metal type for a printing press, consisting of fifty of each vowel and twenty of each consonant. This project becomes the test for his adulthood in the Smithing Guild, and upon its completion, Myne bestows upon him the title of Gutenberg, making him the first person to hold that name. His coworkers would subsequently tease him with the nickname, which eventually stuck. While he weeps tears of joy upon realizing his life's work will be dedicated to printing, he also finds relief in the few commissions from Myne that are unrelated to the monotonous task of forging letters.

Johann’s relationship with his patron, Rozemyne, is the central pillar of his development. As she is his only patron, his professional fate is almost entirely tied to her whims and demands, which are often unconventional and relentless. This pressure, however, forces him to constantly hone and refine his skills. He also has a competitive but respectful dynamic with another craftsman named Zack, who envies Johann’s prestigious title and patronage. In his personal life, Johann becomes engaged to the granddaughter of his former foreman, though this relationship is later complicated by her growing interest in a more sociable apprentice named Danilo. The foreman ultimately supports Johann leaving Ehrenfest to follow Rozemyne, seeing little future for him without her patronage, which further contributes to his feelings of depression despite his loyalty to his patron.

Throughout the story, Johann undergoes significant development. He begins as a struggling apprentice with no patrons and little confidence, but through his work on the printing press, he grows into an indispensable pillar of the printing enterprise. His perfectionism, once a hindrance, becomes his greatest asset under the direction of a patron who values quality above all else. His most notable ability is his exceptional precision in metalworking, which allows him to create items of a quality no other smith can match, such as the tiny metal type required for printing and precision knives for cutting stencils.