The herdsman, whose name could not be identified, reportedly chopped off the head of the woman with a machete.
She was reportedly attacked near a stream where she had gone to fetch water with her younger sister.
The assailant was said to have ambushed the woman while she bent down to collect water from the stream and took to his heels.
But he was arrested after her younger sister reported the act to the police.
Information by the residents, including the traditional ruler, the Alasa of Ilasa, Oba Ajayi Omolagba, reveal that the woman had been allegedly handed over to the suspected assailant as a future wife while she was still a teenager, in consonance with their custom and tradition.
But trouble started last month when the suspect allegedly requested the woman to spend the Eid el-Fitr with him.
The failure of the family of the young woman to release her before, during and after the celebration angered the suspect.
He was said to have assumed that the contract had been breached by the family and hence the dastardly act.
Another report says the lady, after growing up, noticed that the “husband” was a drunkard and drug addict, thereby avoiding him.
Some relatives of the deceased, who did not want their names mentioned, expressed sadness and shock over the incident.
They said the suspected murderer made a request to spend the Eid-el-Fitr with his wife, adding that the lady was supposed to go to him the next day before he killed her.
Addressing reporters, Oba Ajayi Omolagba condemned the incident, saying the community had been in shock since the incident occurred.
The monarch said the families of the parties and their landlords had been summoned to a meeting where resolutions were reached on how to forestall future occurrence.
Police spokesman Caleb Ikechukwu said investigation had been launched to unravel the cause of the criminal act.