A man left his friend's lifeless body in a pond and went home for a sleep after "accidentally" killing her during sex in the woods, he told a court.
Wesley Streete returned to cover Keeley Bunker's body in branches in Tamworth, Staffordshire because he was "scared people would find her".
The 20-year-old was later found dead by a search party, Stafford Crown Court heard.
Mr Streete, 20, of no fixed address, denies rape and murder.
The trial has heard that Ms Bunker regarded Mr Streete as a trusted friend when he walked her home after her birthday celebration in Birmingham in the early hours of 19 September.
Giving evidence on Tuesday, Mr Streete said he previously lied about what happened because he was "scared" and denied deliberately killing her.
His barrister Rachel Brand QC asked him: "When Keeley Bunker died, did that happen in Wigginton Park? Were you with her?"
"Yes," he replied, to both questions.
Asked how she died, Mr Streete replied: "I put my arms around her neck and accidentally killed her. We were having sex."
Asked why he told "lies about what had happened", Mr Streete said: "I didn't know how to act and explain to other people how she died because I felt embarrassed in myself and very scared, to explain to police - everyone."
The defendant said he and Ms Bunker had "started flirting" and began kissing and being intimate in the park, during which he said she had seemed "happy".
He claimed CCTV footage played earlier in the trial featuring the pair near a park entrance had shown them "play fighting".
Answering his barrister, he denied Ms Bunker was trying to "get away" or "run away" from him.
He said it was after the footage was captured that they went back into the park and had sex.
He told the court he "started to panic" after Ms Bunker "went floppy". He claimed he checked for a pulse but said it did not enter his head to call police.
Instead, he said he "put her in the pond", telling the jury "my head was in a mess".
The court heard he returned to the body "quite a few times" throughout the day to cover Ms Bunker with more branches.
"The last time I was stood there, I was just thinking 'why me, I didn't mean for this to happen'," he said.
Mr Streete also denies two further charges of rape, three counts of sexual assault and a charge of sexual activity with a child, against three other victims, all said to have happened in previous years.
The trial continues.