Speaking after Thursday night's Europa Conference League defeat to FK Qarabag, he said: “The biggest thing is coming somewhere you want to – and playing games.
“This seemed the perfect place for me.
“I was straight up on Thursday. It ended up being a six-and-a-half-hour drive, which wasn’t great, but at least I got here. I got to see the stadium rocking, the fans were unreal and I’m really happy to be here. It was unbelievable. Obviously it was the first time I’d seen the stadium, and the fans were great. Hopefully there’s more of it this season.
“The manager used to play for Newcastle, and I’ve heard great stuff about the club, and the football they play. He’s experienced Newcastle, knows what it’s like, and I’m really looking forward to working with him and his team.”
Longstaff spoke to United team-mate Ryan Fraser, an Aberdonian who started his career at Pittodrie, before joining the club.
“I spoke to Ryan Fraser, who obviously came through the set-up here, and he just said it was a great club and if you get the chance go and play there,” said Longstaff. I didn’t need much persuading other than that.
“What you want as a player is to be playing under pressure and to deal with it. At Newcastle there’s an expectancy to play at a high level. I’m expecting the exact same thing at Aberdeen.
“Whether that’s playing a little further back and getting on the ball, or whether it’s breaking into boxes and scoring goals, I’m happy to do either.
"Like he said, if I can chip in with a few goals, it’s going to be great, so I’m looking forward to it.”
We’ve gathered the best of today’s Premier League speculation below…

. LONDON, ENGLAND - AUGUST 21: A detailed view of the Nike Strike Aerowsculpt Official Premier League match ball is seen during the Premier League match between Crystal Palace and Brentford at Selhurst Park on August 21, 2021 in London, England. (Photo by Julian Finney/Getty Images)
Nike Strike Aerowsculpt Official Premier League match ball. (Photo by Julian Finney/Getty Images) Photo: Julian Finney

. GLASGOW, SCOTLAND - JUNE 14: Ryan Christie of Scotland reacts as he inspects the pitch prior to the UEFA Euro 2020 Championship Group D match between Scotland v Czech Republic at Hampden Park on June 14, 2021 in Glasgow, Scotland. (Photo by Stu Forster/Getty Images)
Ryan Christie has agreed personal terms with Bournemouth despite a late bid from Burnley as the Cherries look to win the race for the Celtic star. (Football Insider) (Photo by Stu Forster/Getty Images) Photo: Stu Forster

1. GLASGOW, SCOTLAND - JUNE 14: Ryan Christie of Scotland reacts as he inspects the pitch prior to the UEFA Euro 2020 Championship Group D match between Scotland v Czech Republic at Hampden Park on June 14, 2021 in Glasgow, Scotland. (Photo by Stu Forster/Getty Images)
Ryan Christie has agreed personal terms with Bournemouth despite a late bid from Burnley as the Cherries look to win the race for the Celtic star. (Football Insider) (Photo by Stu Forster/Getty Images) Photo: Stu Forster

2. Rovers still want Khadra
Championship side Blackburn Rovers are finally closing in on a season-long loan move for Brighton winger Reda Khadra. (The Athletic) (Photo by Clive Brunskill/Getty Images) Photo: Clive Brunskill

3. Clarets interested in Booth
Premier League side Burnley are interested in a loan deal for Bayern Munich and United States youth international Taylor Booth. (ESPN) (Photo by Srdjan Stevanovic/Getty Images) Photo: Srdjan Stevanovic

4. Albion keen on Niasse
Brighton are battling it out with Sheffield United to sign Lille midfielder Cheikh Niasse on loan. (La Voix du Nord) (Photo by JEAN-CHRISTOPHE VERHAEGEN/AFP via Getty Images) Photo: JEAN-CHRISTOPHE VERHAEGEN