Johannes
The Seducer named in the title, Johannes is the owner of the diary and the protagonist of his own story. He is twenty-six and of unknown employment, but from his writing we can tell he is highly intellectual. Both charming and calculating, he is very capable of social maneuverings and takes full advantage of it. Though Johannes himself never mentions any prior conquests, his complex personal aesthetic doctrine seems to be informed by past seductions. Quite unconcerned with the unaesthetic consequences of his actions, Johannes is practically amoral. In addition, he is resolute in his seduction of Cordelia and nearly always has things his way, though he is equally determined to resist satisfaction. He is melancholic, but often finds himself in fits of ecstatic dreaming and reflection. His greatest sources of pleasure, then, are in painstakingly crafting "interesting" situations and thereafter reflecting upon them.
While it is tempting to do so, Johannes cannot be analyzed psychologically. Rather, he is read as a philosophic embodiment of aestheticism, with all its attractive and disquieting attributes. Johannes is particularly associated with the shadowy, predatory side of aestheticism, which selfishly sacrifices anything in order to feed a hunger for "the interesting."
Cordelia Wahl
The object of Johannes' seduction, Cordelia is the victim of Johannes' designs and duplicity. She is sixteen years old and very beautiful, according to Johannes. Both her parents having passed, she lives with her two sisters and her aunt in Copenhagen. Prior to meeting Johannes, Cordelia appears to be kindhearted, but not simple. This is exactly what Johannes finds to be ripe conditions for seduction: he exploits her imaginativeness and emotional eagerness. By the end of the diary, her emotions are assaulted to the point of devastation. She becomes filled with consternation and is deeply divided on how to make sense of what Johannes has done to her.
It is impossible to obtain an objective picture of Cordelia, as the entire diary is a sort of poeticization of his acts and their results. Even so, through her three notes in the beginning we can infer that she was once quite happy in her simple love, and that after Johannes' manipulation of her she has been left with deep conflicting emotions. She is naturally beautiful, but for Kierkegaard, the destruction of Cordelia represents the dark products of pure aestheticism.
Edward
A wooer of Cordelia, Edward is close to her in age and falls in love with her. He is romantic in a traditional sense, but is unsure about how to proceed with courting Cordelia. As such, he is easily manipulated, and Johannes acts as his confidant and counselor in order to get closer to Cordelia.
Aunt Jette
Cordelia's aunt and caretaker, Aunt Jette is the head of the Wahl household. She is, however, easily deceived by Johannes. As her guardian, Aunt Jette is the one Cordelia refers Johannes to when he proposes, since she is too taken aback to make a decision. Like every other character in the diary, she is taken advantage of by Johannes in order to facilitate his seduction of Cordelia.
