Johnson told the jury that he had texted the teenager from a hotel room, explaining that spending so much time in hotels can get boring and you need to "keep yourself busy".
"I spent a lot of time in hotels, it's easy to get carried away", he said. "I was in a hotel room and I was bored. I know I shouldn't have been doing that."
He said his messages to the teenager were "flirty" and "inappropriate".
Johnson said that while he was texting the teenage girl saying "you owe me" for signing a Sunderland shirt, his girlfriend was in bed.
Asked how he now feels now about the messages he sent her, he mumbled "embarrassed" adding "should not have ever done them".
Speaking about the teenager, he said he was "attracted to her".
The jury was read out a series of messages exchanged between Johnson and the teenager, in which they discussed their next meeting and he asked her "am I only getting a kiss?"
She replied: "Depends on what else you're after" and he then said "I dunno, it depends what you are up for.. a little bit more than a kiss".
The teenager wrote: "Like?" And he said: "A bit of feeling. Just see. No pressure. Lol", adding: "Keep deleting our convos".
Asked what he meant by "a bit of feeling", Johnson told the court that this was "stupidity from me", adding: "I really regret writing that".
Asked whether he thought there was a possibility of touching the teenage girl sexually at their next meeting, he said: "Yeah, there was a possibility".
Asked if wanted this to happen, he replied "Yeah".
He said he thought their meeting would last 10 to 15 minutes, adding: "I never thought the kiss was going to happen."
Johnson said that he did not know the teenager was taking a video while they were sitting in his car during their second meeting.
"I knew she had a phone, but I didn't know [she was filming]," he said
He said that during the meeting, they were talking for "almost all of the time" about football. He said the atmosphere was "similar" to how it had been in their first meeting when he gave her a signed shirt.
Asked if he wanted to kiss the teenager, he said "yes". Asked if he enjoyed kissing her, he replied "yes".
Explaining where his hands were during the kiss, he told the jury "they were just sort of resting sort of on her" which was in order "to give me stability when I was leaning over to kiss her".
Johnson described what he was thinking while he and the teenager kissed. "I had all sorts of things going on in my head," he said.
He said he was worrying that they were in "quite a populated area" and that someone would see. He said he "wasn't thinking clearly".
The footballer said he did not turn the car around at any point, adding that "it would have been a better idea to do that when I was kissing her".
Afterwards, when he was at the stadium, he texted her saying: "haha think we need to go in the back next time", the court heard.
The trial of Adam Johnson has now adjourned for the day - but it is not the footballer's last day in the witness stand.
His defence barrister will complete the questioning of his client tomorrow morning, before Johnson's cross-examination by the prosecution.
Court starts again tomorrow at 10.30am - join us then for the latest updates
