Okonkwo is a hypermasculine warrior, a leader with a few titles in his tribe in Umuofia, and he is no beginner when it comes to killing. However, both the killing of Ikemefuna and that of Ezeudu's son feature prominently in Okonkwo's character development in the novel.

Ikemefuna is a boy taken from another village—basically as a hostage. He is not killed right away, though and grows up next to Okonkwo's eldest son, Nwoye, for three years. Okonkwo comes to like the boy (more than his own son, really), but he is determined to go along when the Oracle decrees that Ikemefuna is to be taken beyond the village limits and killed. He is advised against doing so, but Okonkwo is afraid of looking weak. When the sacrificial killing begins, as one of the tribesmen cuts Ikemefuna from behind, the boy looks to Okonkwo and calls him father.

Okonkwo is emotionally affected, but instead of showing his grief, he decides to take his machete and finish the killing himself. This is seen as extreme and harsh to his fellow tribal leaders. Okonkwo feels out of sorts for a while after the boy's death, but his public demeanor leads people to think he is heartless and unaffected. While Okonkwo's act is frowned upon by other leaders, he has technically not committed a crime because he was following the Oracle. He is not officially punished for this act.

The killing of Ezeudu's son, on the other hand, is totally accidental. He is at the funeral of Ezeudu with the rest of the village and one of the shots he fires from his gun accidentally hits and kills one of the sons as he is participating in one of the funeral rituals. This is labeled a "feminine crime" because it is unintentional. Okonkwo is exiled for seven years to his mother's village, Mbanta. Clearly, this act of committing a "feminine crime" is ironic, since Okonkwo cares more about maintaining his masculinity in front of others than anything else. In the killing of Ikemefuna, for example, his action is motivated by his desire to not be "thought weak."

Based on these examples, the law in Igbo culture is based on the society's perception of the gods. The fact that Okonkwo is exiled is aligned with the belief that his unintentional killing is "an offense on the land" which then has to be cleansed. It is considered just that Okonkwo be sent to his motherland for committing the "feminine crime" and that he must stay away from his village for seven years to allow the land to be cleansed.

Ikemefuna is given to the village of Umuofia from Mbaino as a sacrifice for the unjust killing of a woman. Okonkwo becomes Ikemefuna's guardian, and Ikemafuna develops into a beloved member of Okonkwo's family. Tragically, the Oracle decrees that Ikemefuna must be killed and instructs Okonkwo to not play a role in the boy's death. However, Okonkwo disobeys the Oracle by killing Ikemefuna in order to not appear weak in front of his peers. Okonkwo is not punished for his role in Ikemefuna's death but suffers from a guilty conscience. In contrast, Okonkwo accidentally kills Ezeudu's son during a funeral service. Okonkwo's action is considered a female crime against the Earth goddess and he is exiled for seven years.

The nature of law and justice in the Igbo society is founded on the longstanding cultural traditions of Umuofia. In the Igbo society, oracles have notoriety and exercise their authority, which is why Ikemefuna must die. There are also crimes that offend various gods and goddesses. Although Okonkwo's action is punishable in Western society, his seven years of exile results from offending the Earth goddess in Igbo society. Overall, Achebe portrays the law of nature and justice in Igbo society as complex and significantly intertwined with traditional beliefs. Western audiences are often perplexed by the Igbo society's system of laws, which can seem either reasonable or unjust depending on the situation and circumstance.

In chapter 7 of Things Fall Apart, Okonkwo kills Ikemefuna. Ikemefuna was given to Okonkwo's village to be sacrificed. Sacrificing ikemefuna would prevent war between these two neighboring clans.

For three years, Ikemefuna lives in Okonkwo's household. Ikemefuna has become part of the family. Okonkwo amd Ikemefuna love one another as father and son. Because of the traditions of the Ibo Society, Okonkwo has to witness and even participate in the killing of Ikemefuna. Okonkwo is afraid of being thought of as weak; therefore, he cuts ikemefuna down with his machete. 

Okonkwo's son, Nwoye, is extremely troubled by such a tradition as the killing of Ikemefuna. Nwoye cannot understand how his clan could be so cold.

While it is perfectly accepting to kill Ikemefuna, the accidental killing of Ezeudu's son is another story. In chapter 13, Okonkwo accidentally shoots Ezeudu's son during a funeral service. Okonkwo's gun accidentally fires. Nonetheless, Okonkwo has to pay a severe penalty for accidentally killing Ezeudu's son. He is banished from his clan. He has to uproot his family and move to his mother's homeland:

It is a crime against the Earth goddess to kill a clansman. There are two types of crimes, male and female. Okonkwo has committed a female crime because the murder is an accident. Nevertheless, he is forced to flee from the clan. He may return after seven years.

Again, the traditions of the Ibo are strange. It is Okonkwo's duty to kill the innocent boy Ikemefuna, but he is cursed when he accidentally kills one of his own tribesmen. It makes no sense to Nwoye, and the nature of justice in Ibo society will likewise seem skewed to readers of the novel.