He had been in London since 2013, but admitted that he's wanted to return to Spain since last year and he's relieved to have made his wish come true.
"I've always hoped to play here and finally I'm a Real [Sociedad] player," Monreal said.
"I've come here with a lot of desire. Despite my age, I'm very competitive and I'm still thinking about achieving my goals."
"Last year it wasn't possible," he explained.
"It was Emery's first year, he was blunt and said I wasn't leaving so it stopped everything.
"This year Unai insisted that I'd continue, but I've been away from home for eight years, and of course family influences you.
"I wanted to come back. It hasn't been easy to leave Arsenal, who I love like few other clubs, but La Real are one of the clubs that I've wanted to play for.
"I'm very happy here and this is where I want to be."