Hawker, 22, was found dead in a sand-filled bathtub on the balcony of Tatsuya Ichihashi's apartment in Chiba, east of Tokyo, in March 2007.
Ichihashi, 32, is charged with murdering the English teacher who worked at a private language school on the East Asian island.
The accused man - one of her students - was arrested in Osaka, in western Japan, on November 10, 2009 and has been in custody since.
He made the confession during the opening of his murder trial in Chiba, Japan, where he knelt on the floor and bowed towards Miss Hawker's family who sat in the court.
'I did not intend to kill her, but I am responsible for her death,' Ichihashi told the court.
'I am very sorry for what I did.'
The defense argued that Ichihashi tried to revive Hawker after suffocating her by accident in an attempt to keep her from crying out for help from the neighbors.
Ichihashi, however, admitted to tying her up and raping her. Read More