The irony of gender
The central irony of the novel is that by pursuing the female attention and love from Mrs. Ota or Fumiko, the protagonist is attempting to justify himself as a male in the likeness of his father. That is, he believes that female love will make him feel masculine, self-sustainable, and powerful. But instead he ends up caught in a spiral that leads the opposite direction than the way he would have hoped.
The irony of romance as a give/take
Another central irony of the novel is that Kikuji seems to believe that what he is doing constitutes romance or maybe even love. But as the novel clearly indicates through the plot, Kikuji is not healthy. His dependence causes him to view love as a thing to be taken from someone else, and when he finds that his own father trusted a specific woman for that task, that's what he tries too, but to no avail. Love must be freely given and never demanded.
The Oedipal irony
The Oedipal aspect of this narrative is that Kikuji's emotional turmoil stems from a thirst for his own mother and a sense of competition with his father. This can be seen in his tumultuous relationship to masculinity. To believe true, balanced things might have made him able to cope with his father's loss, but instead, he doesn't view his father's life as a part of his own inheritance, so he tries to find it by looking for his mother in his relationships to women.
The irony of tragic loss
The main loss in this novel is the death of Kikuji's father, and the irony is that he spends the entire novel trying to undo the effects of the loss. His inability to function after the tragedy is an indication of an ironic need to live in a world where everything dies.
The irony of the daughter
In the section of the novel called "Her Mother's Lipstick," Kikuji attempts to justify the new loss of Mrs. Ota's suicide by transferring his need onto her daughter, and the irony is actually kind of disturbing. His blinding need for emotional security in his sexuality causes him to complete ignore the fact that the daughter is as distinct from her mother as he is from his father. He has something in common with her, the loss of a parent, but instead of seeing that similarity as a breeding ground for community, he sees it as an entitlement. The core irony of the novel with regards to its dark subject matter is that Kikuji is suffering because he is evil, not because he is alone. Actually, he's not alone. He feels alone because he has a perverted view of love and attention.
