The £2million left-sided midfielder finally completed the transfer from Stromsgodset more than a month after he first got word Celtic were interested in signing him. However, any suggestion the 23-year-old has been brought in as a replacement for the soon-to-be-out-contract Welshman is quickly shot down - by the new arrival himself.
Johansen has made it clear he does not expect to walk straight into a starting spot
in Neil Lennon's side. He is ready to fight for his place - and he would be delighted if Ledley can agree a new deal and stick around to be one of the men challenging him for a midfield role.
He said: "Joe is a good player, and everyone wants to keep good players at their club.
"But I am here to make my way into the team. I don't want to sit with the crowd or sit on the bench.
"Everybody wants to play in the first XI, and that's my goal, to come in and try to do that."
Johansen, who met his new team-mates for the first time yesterday and will start training with them today, admits he will need a little time to get his fitness up to the required level, having last played in mid-November as Stromsgodset clinched the Norwegian title.
But he is aiming to be in the best possible shape to meet the challenge which he knows he now faces as he pursues a second league winner's medal in one season.
"I don't expect to walk straight into the team, and that's the way it should be," said the Norwegian international.
"At a big club like this, of course there is competition for the places.
"That makes players better because in every training session you have to be a 100%.
"Everything you do has to be the best you can do it. Everyone wants to fight their way into the team and, of course, I will be the same. But I'm looking forward to that."
Lennon has landed a very hungry player who explained: "I improved a lot last season.
"2012 was a good year for me, but last season I had pressure on me when the fans and the media expected something from me.
"I had to prove I was capable of doing the same again.
"We won the title and I made my debut in the national team, so it was a fantastic season for me.
"I really hope to continue that, so I'll work even harder here.
"I'm a passing player, but you can't just stand and pass the ball.
"You need to create something also, and I hope to score goals, take free kicks and make assists."