Nakagawa lost a Japanese/OPBF Middleweight title unification bout to Akio Shibata (22-8-1, 9) and is said to have retired immediately after the bout.
Aged 36 Nakagawa's retirement did look likely to be sooner rather than later and it's probably fair to suggest that the loss to Shibata acted like a catalyst for the decision. Had he won we don't imagine he'd have retired though with his reactions slowing it did seem that he was, at least starting, to look like an old fighter. He was "shot" by any means but he wasn't snappy and he didn't have the energy needed to capitalise on the few openings he was offered.
We would like to wish Daisuke a happy retirement if the story is true and wish him all the best in the future. He was always fun to watch with his venomous power and he had an incredible career winning Japanese titles at Welterweight, Light Middleweight and Middleweight whilst scoring notable victories over Koji Numata, Akinori Watanabe and Tomohiro Ebisu.
(Picture thanks to Teiken promotions)