Mentorship and Education
The relationship between the narrator and Sensei, the central relationship in the story, is one of student and, literally, teacher, though a very unconventional one at that. From the very beginning of the story, even before we the readers become aware of Sensei's emotional depth and life experience, the narrator names him as Sensei, and so we listen attentively to what the man says, trying to understand him. In fact, the narrator himself instinctively realizes that Sensei is a teacher figure, even a father figure, for him, which makes him impulsively call Sensei 'Sensei'. As the narrator himself says, Sensei was not an obvious or good mentor in any usual way, especially in comparison to the university lecturers whom the narrator encountered as a student. A man who seems to live against the ideas of the time by squandering his talents in idleness, Sensei gives the narrator sincere advice in life of the sort that he does not find from his other teachers or his father.
Cultural Conflict
The Meiji era inaugurated a period of modernization and Westernization in Japan so rapid that towards its end, when the story takes place, elements of traditional Japanese thinking existed side-by-side the new Western thought. The common people, such as the narrator's family and Sensei's wife, continued more or less to live by the same duty-intensive Confucian code, but those of the intelligentsia, that is to say those who received university educations, found themselves forced to reconcile two strikingly different ways of approaching the world. For Sensei, the narrator, and to an even greater extent for K, the influence of the Western ideal of individualism alienated them from their own societies, in which they would otherwise have been comfortably integrated, and so made them painfully lonely.
Misanthropy
Sensei's misanthropy develops from two incidents. The first is his uncle's cheating him of his inheritance; because he and his father had trusted his uncle so much, the betrayal was all the more painful. This shattering of innocence, which Sensei described as an inverse of the moment when an adolescent boy sees beauty in the world, especially in women, combined with a budding doubtful nature that Sensei already had, made him turn against the toward with great distrust and disdain. Nevertheless, he still retains confident in his own virtue, until he himself commits a terrible act of betrayal, which makes him hate the entire world, himself included.
Vengeance
The narrator is shocked when Sensei admits to him that he has a vengeful nature, because it seems contradictory that such a loving and calm man could also harbor such feeling. In the first case, Sensei feels vengeful when his uncle cheats him of his inheritance; but although he considers suing him, he ultimately decides not to so that he does not interrupt his studies. Nevertheless, this ill will does not leave Sensei: it ends up transforming into his misanthropy. Also, his desire to hurt K after hearing K's confession of love for Ojosan comes from a feeling not only of being betrayed by a friend whom he tried to help but also of being an inferior to him.
Loneliness and Love
Sensei tells the narrator that youth is both the loneliest time in one’s life, and also a time when one searches for love. In the case of the narrator, he feels loneliness due to his alienation from his family and he pursues love through his friendship with Sensei, though the story is not concerned with the narrator's romances, if there were any. Sensei himself, when he was boarding with Okusan and Ojosan, finds in Ojosan not an intellectual equal but a vision of beauty -- a beauty that is very much of the past, untainted by modernization. He hopes that he can lose his modern loneliness in this love, but ultimately K will cast the shadow of modernity onto that love.
Humanity
In his arguments with K, Sensei takes the position that K, though he is human, is trying to make himself inhuman. Indeed, the ascetic Buddhist ideals and prideful Western egoism drive K to a kind of impossible ideal, one which he could only come close to attaining by living a miserable life, one which Sensei realizes is sapping him of his health. The change of environment for K into the company of women livens him somewhat, but it brings the unreality, or inhumanity, of his ideas into a state of direct contradiction with reality, which causes his personal crisis. Sensei’s argument against inhumanity is not a critique specifically of modern thought, but rather of any thought that denies the beauty of life.
The End of an Era
Although the novel deals with many timeless issues, it is very much grounded in the historical context of the late Meiji era. After the Emperor Meiji dies, those who grew up in the era of his rule and the modernization that characterized it find themselves left behind by the next generation, which is far more native to the modern world than they are. K's suicide is an admission that it is impossible for a Meiji era man to reconcile his traditional and modern beliefs, and Sensei's suicide, though it holds a very similar meaning, also comes from a sense of atonement and respect for the time.
