[2] Nagashima spent three years competing in domestic Japanese races before getting selected for the World Cup sprint event in Nagano in December 2004.

Nagashima started the 2006 season by winning his first domestic medal, taking bronze at the Japanese 2 × 500 championships, 0.610 points behind Joji Kato.

Nagashima went home in December, forgoing the sprint World Cup race in Inzell like many of his compatriots, to win the Japanese sprint championships held in the last weekend of December 2005, tallying 141.985 points to finish just over 0.05 points ahead of silver medallist Yusuke Imai.

Nagashima then travelled to Turin and the 2006 Winter Olympics, but failed to place in the top ten, ending 13th as the third best Japanese skater, nearly 1.5 points behind winner Joey Cheek on the 2 × 500 metres.

First, he won both the 2 × 500 and the 1000 metre events at the Japanese Single Distance Championships in October, thus allowing him to go to Thialf, Heerenveen, for the opening World Cup races.