Sensei's Love and World-Weariness
One of the central paradoxes in the story is how Sensei can at once hate the world and love his wife. After the trauma of his uncle's betrayal, his nascent doubtfulness intensified to the point that he even suspected Okusan of having ulterior motives for encouraging his marriage to Ojosan. Nevertheless, his love for Ojosan absolute and as such almost otherworldly; in fact, Sensei considers his wife to be such a pure soul, untainted by worldly imperfections, that he cannot bring himself to tell her the truth behind his melancholy and so assuage her constant worries for him.
Sensei's Wariness Towards the Narrator
The narrator realizes early on in his relationship with Sensei that the older man never candidly reveals his past and that despite the narrator's sincerity in asking questions, Sensei feels a certain measure of wariness, even fear towards the narrator. Considering Sensei's reclusiveness and misanthropy, his willingness to often meet with the narrator indicates that he places an unusual amount of trust in him. Nevertheless, Sensei can never fully trust anyone, and so it is not until he has decided to die that he is able to reveal his whole personal history.
The Emptiness of Education
When the narrator talks with Sensei's wife, a paragon of the traditional Japanese wife, both of them notice the sharp difference between their mindsets. With his Western-influenced university education, the narrator is eager to analyze and understand things, but Sensei's wife relies more on an intuitive sense to approach the world and is comfortable with leaving certain stones unturned. Their respective attitudes towards Sensei is illustrative of their ways of thinking: the student constantly asks incisive questions about his past, while Sensei's wife does not press him when he refuses to answer. Oftentimes the narrator realizes that his approach has been the inferior one. Moreover, when he returns home, he finds that his new acquired mindset has done nothing for him but to alienate him from his family.
Sensei's Self-Dissection
Even though Sensei seems to fear nothing more than the narrator's or his wife's unearthing his disreputable past and then analyzing his personality, Sensei shows in his testament a keen ability for picking himself apart in introspection. Often after writing of a certain past action he took, Sensei tries to figure out his what his motives, conscious or unconscious, may have really been. In the end, he represents the total of these reflections to the narrator as his life story but also as a kind of psychological case study.
