This should be the 1st Japanese mystery/detective novel that I've read in English (instead of Chinese). Interestingly, Shimada Soji（島田莊司）wrote an "Introduction" for this novel in its apparently first English translation. It's also interesting for me to read about the discussion of this novel establishing the style/epoch of "shin honkaku" or "new orthodox" (新本格推理) in English, though there is nothing surprising as the content is the same as what I've read in Chinese translation.
I didn't quite understand the ending (the green glass bottle with pieces of paper) in the waterfront at first. Then, after reading the prologue of the novel again, I finally remembered and realized that Morisu (the murderer) put the "letter of confession" (p.17/6th line) in the bottle and threw the bottle into the dark sea at the very beginning. He left the judgment to the sea or the God. So, when he asked a boy to give the bottle to Shimada Kiyoshi, it seems that he's probably decided to follow his conscience or fate to confess.
In this novel, we don't really have a super-detective who has solved all the mysteries for us, even though Ellery (Matsu'ura Junya) and Shimada Kiyoshi both did do some detective works. Instead, it's the murder who has finally revealed what's happened on the Island Tsunojima. At the end of page 196, when Morisu told Inspector Shimada: 'I'm Van Dine.', I didn't immediately understand that the mystery has been disclosed. I somehow couldn't believe or didn't immediately realize that Morisu was the "Van" on Tsunojima and I wondered whether there were two 'Van Dine' in the Mystery Club of K--- University. But after flipping a page or 2 and realizing that only 6 out of 7 students died on Tsunojima, I finally understood and accepted that Morisu had been the murderer and moving between the Mainland and the Island in all those nights. Stupid me !
p.58 (25th line): "... I think can detect ..." should probably be "... I think I can detect ..."....Continua