Mr Watanabe, who is now 72, had been drafted into the Japanese army in 1944 and was on a ship from Java to Singapore when it was attacked by a British submarine.
He felt the shock of the torpedo hitting the side of the ship and then - nothing. It failed to explode. It was like walking away from a firing squad after a last-minute reprieve.
Another torpedo struck the ship closer to the bow, however, and the ship went down. Mr Watanabe was able to stay afloat long enough to be saved, but one of his friends died. He thought it was ironic that he was telling this story - the biggest story of his life - to a correspondent for a British newspaper, 50 years afterwards. 'I would never have thought I would be doing this,' he said, straining to smile.
Mr Watanabe thought he was risking his life to fight a just war. He, along with the rest of Japan, had been told by the military government that they were liberating Asia by expelling Western imperialists. And like many veterans of what Japan calls the 'Pacific War', in which 2 million Japanese and 15 to 20 million others died, he strongly objects to the decision of the new Prime Minister, Morihiro Hosokawa, to admit officially that it was a war of aggression, for which Japan must apologise.
Mr Hosokawa's indication last week that his government would apologise for the war after half a century of prevaricating has sparked a heated debate in Japan. For some it is an opportunity to come to terms with the past that has dogged Japan's relations with Asia for 50 years. For others, Mr Hosokawa is entering into a taboo area of the national psyche still troubled by feelings of shame and damaged honour. At the annual ceremony to commemorate Japan's war dead at Yasukuni shrine in Tokyo last Sunday, banners called for Mr Hosokawa to resign, and people said aloud he was a disgrace and a traitor.
Two cabinet ministers have objected to Mr Hosokawa's remarks, and a national daily newspaper angrily attacked what it termed moves 'to convict Japan based on a one-sided interpretation of history'. Extreme right-wing nationalists have been the most vocal in criticising the Prime Minister, but veterans' associations have also made known their displeasure.
Masanori Tsukagoshi was based on the southern Japanese island of Kyushu during the war, supervising the dispatch of bombers. He has bad memories too: many of the pilots he knew never came back from their missions, and some of his friends from schooldays became kamikaze pilots. Now in his seventies, he said he is only just beginning to talk about his experiences. 'My generation has not been accustomed to speak about the war. We just stayed silent. But now I am retired I have more time to think about it.'
Mr Tsukagoshi did not like what Mr Hosokawa said about Japan waging an aggressive war. 'At the time I did not think it was an aggressive war. I thought it was a good thing. Now when I look back, I cannot deny that it was a war of aggression, that the Japanese army was trying to colonise Asia in the place of the West. But Hosokawa's comments are too simple - at the time we believed it was a just war.'
In a culture where losing face is to be avoided at all costs, apologising and admitting one was wrong is a highly sensitive issue. For Japanese war veterans Mr Hosokawa's calling the conflict 'a war of aggression and a wrong war' is seen as dishonouring the country's own war dead. On the other hand, if the apology is left unspoken, their honour is kept intact - even if everyone knows in his heart that a wrong was indeed committed.
'Japan was defeated, so justice does not make any sense,' said Mr Watanabe. 'After the war, the US started the (war crimes) trials, so it was their justice. If Japan had won the war, the facts would have looked different. Because we lost it is easy to criticise us. So I don't think we should make a complete apology.'
Both Mr Watanabe and Mr Tsukagoshi accept the argument that for Japan to play a larger diplomatic role in Asia some form of reconciliation with their neighbours will be necessary. But still they could not swallow the perceived dishonour in an outright apology.
'I was talking to an old guy in a restaurant last night,' one of them said. 'He was saying that if everything that people did then is disowned, then why did kamikaze pilots die for the nation? So I doubt that everyone can agree with Mr Hosokawa.'
Tomorrow: Facing up to history