Because Okonkwo have to kill him because the Oracle decreed that Ikemefuna must die:)
The Oracle of Agbala pronounced that Ikemefuna must die.
The earth goddess is associated with fertility, nature, and balance in Igbo culture. In the story of "Things Fall Apart," the earth goddess plays a symbolic role in Okonkwo's story as his tragic downfall is connected to his defiance of traditional customs and his role in Ikemefuna's death, which angers the earth goddess and disrupts the natural order of the community.
Ikemefuna is taken from his village as part of a settlement for the death of a Umuofian woman in the marketplace of his village. He goes to live with Okonkwo. Later, Ikemefuna is sentenced to die, but he does not know it.
The Oracle of the Hills and the Caves pronounced that Ikemefuna must die, so they meekly followed their gods' orders.
The Oracle of the Hills and the Caves decreed that Ikemefuna should be sacrificed as compensation for the murder of a woman from Umuofia. This decision was final and carried out by the villagers, including Okonkwo, despite Ikemefuna's close bond with the family.
Ikemefuna is taken from his village as part of a settlement for the death of a Umuofian woman in the marketplace of his village. He goes to live with Okonkwo. Later, Ikemefuna is sentenced to die, but he does not know it.
Ikemefuna is led by the tribe on a long march outside of its lands. One tribeman cuts him with a machete. As Ikemefuna runs to Okonkwo for safety, Okonkwo chops Ikemefuna down with his machete.
Okonkwo becomes a father to Ikemefuna, and Ikemefuna calls Okonkwo father. Ikemefuna is like the second man in the house, the closest to Okonkwo's personality, and helps to develop Nwoye's manhood. Okonkwo likes Ikemefuna, but does not show his feelings towards Ikemefuna because to do so would be unmanly.
The village elders told Okonkwo to take care of Ikemefuna until his fate was decided. When Ikemefuna is sentenced to die, Okonkwo is afraid of being seen as weak. When Ikemefuna cries to him, Okonkwo takes care of Ikemefuna, (kills him).
Ikemefuna came from Mbaino.
Ikemefuna is taken into Okonkwo's home as part of the compensation for a murder committed by the neighboring village. He lives with Okonkwo's family and forms a close bond with Okonkwo's son, Nwoye. However, tragically, Okonkwo ultimately participates in Ikemefuna's killing to demonstrate his masculinity and avoid appearing weak.
In "Things Fall Apart" by Chinua Achebe, Ikemefuna, a boy from another village, was taken in by Okonkwo's family. Eventually, Ikemefuna was killed by the villagers as a sacrifice to avoid retribution for a murder that took place in their village. Okonkwo's participation in Ikemefuna's death deeply affects him and contributes to his own downfall.