The 26-year-old immediately won over the Emirates faithful when he was signed from Celtic in 2019 to replace the long-serving Nacho Monreal, playing a crucial role in Arsenal's FA Cup triumph in his debut campaign.
However, Tierney's North London career has also been disrupted by numerous injury concerns, and he lost his status as first-choice left-back to Oleksandr Zinchenko last season.
The Scotland international was mainly restricted to starts in the Europa League in 2022-23, and both Manchester City and Newcastle United were tipped to battle for his signature in the summer window.
Jurrien Timber's arrival from Ajax pushed Tierney further down the pecking order, and despite coming off the bench in the Community Shield against Man City, he did not make the squad for any of Arsenal's first three Premier League games this term as Arteta shifted to a system with inverted full-backs.
Even with Tierney injured and Takehiro Tomiyasu suspended, Jakub Kiwior was preferred against Fulham on August 26, while Zinchenko has now returned to full fitness following a calf problem.
As a result, Tierney secured a late move to La Liga outfit Sociedad in order to increase his game time, and he made his debut for Imanol Alguacil's side in a 5-3 win over Granada on September 2, playing 69 minutes of that eight-goal thriller.
The defender also remains a stalwart of Steve Clarke's Scotland team and started alongside Ryan Porteous and Jack Hendry in a three-man defence during Tuesday's 150th Anniversary Heritage match against England, who won 3-1 at Hampden Park.
Tierney reunited with Gunners colleagues Bukayo Saka and Aaron Ramsdale in midweek, but he confessed to the Daily Record before that friendly that he found it easy to leave North London behind for a new challenge in a new country.
"Was it a hard decision? No, it was an easy decision. It was a big decision, but an easy decision. Clearly it's a big change for me," the left-back said.
"Culturally, the league, the language, everything is different. But I think you have to embrace it and put yourself in uncomfortable positions sometimes. You just have to enjoy it, go make the most of it and learn everything you can. I want to grow as a person and grow as a player and that's my ambition.
"I will always be a home boy. I always love Scotland and after my career is done I will always live in Scotland. But you only get one shot at this. I had the opportunity to go to La Liga and it was one I really didn't want to turn down.
"I took the chance and so far I'm enjoying it. I am in a really good place now. I'm enjoying it over there in Spain. I was buzzing to get the move done. I am really enjoying it."
Real Sociedad do not possess an option or obligation to sign Tierney on a permanent basis, and the Scotsman is therefore due to return to Arsenal - where his contract runs until 2026 - at the end of the season.
Tierney has scored five goals and set up 14 more in 124 matches for the Gunners across all tournaments and could potentially face his parent club in this season's Champions League, as Sociedad gear up for their Group D opener against last year's runners-up Inter Milan on September 20.