Anti-whaling campaigner Pete Bethune of New Zealand has told a court in Tokyo that he is not an enemy of Japan.
In a statement on the final day of his trial, he apologised to the crew of the Shona Maru 2 for causing trouble.
He said he did not intend to injure any crew members, but took action because he wanted to stop Japan's illegal whaling. He described whaling as "very cruel".
Mr Bethune, 45, is facing five charges after he boarded the Japanese ship in the Southern Ocean in February.
He has pleaded guilty to four charges, but has denied one of assault.
Prosecutors have demanded a prison sentence of two years.
A verdict is due on 7 July.