Mengistu, an Israeli of Ethiopian descent, left his home in Ashkelon on September 7, 2014. He then walked to Zikim beach on the Gaza border, and crossed the security fence between Israel and the Gaza Strip.
After Mengistu crossed the border, he was detained and interrogated by Hamas and has been missing since then and his fate is unknown. Hamas is also holding the bodies of Hadar Goldin and Oron Shaul, IDF soldiers who fell in Gaza during the 2014 war, as well as fellow Israeli national Hisham al-Sayed.
Mengistu's brother Ilan told Ynet that family is suffering greatly due to his abduction.
"Even today, years after the incident, we do not have any new information on Avera," said Ilan. "This frustrates us more with every passing day."
"Every passing year I tell myself, that maybe this year it will happen, maybe Avera will return this year. I still hope so," he said.
"The pain is the same pain that has been with us for five years. We know that there is no choice, we must save him, bring him back from there. Unfortunately, there are no constant efforts, there is no new information. Mother prays daily to see him again."
The rally to mark the fifth anniversary of Mengistu's captivity will take place on Sunday evening at 18:30 at Tel Aviv Museum of Art.
The rally was planned under the slogan "Youths Unite for Avera", and will be attended by Mengistu's family, youth movement students, and various organizations from all across Israeli society.
At the start of the evening, the youth will hear the tales of Avera from his family - about his special and lovely nature of a young man who experienced a deep crisis following the death of a beloved brother, his mental deterioration that led to repeated hospitalizations that didn't help and his entrance into Gaza while unaware of his actions, while in front of IDF security cameras.
The protest will also hear about the determination of an Ashkelon family without means as they fought for Avera's freedom and to keep his captivity alive in the minds of the public.