The 23-year-old Samurai Blue striker has decided to move from Kashima Antlers to Germany to the 2. Bundesliga in order to further his development
The transfer of the 23-year-old Japan international was confirmed by Antlers on their official website on Monday morning, who described the decision as an "incredibly difficult" one.
"Thank you for all of your assistance in the last five years," he told the site.
"Antlers have helped me grow up, so this was an incredibly difficult decision to make. However, I eventually came to the decision that I want to place myself in a tough environment in order to develop further as a player.
"I want to be able to play for Antlers again in the future. I'm incredibly grateful for the support of all of our fans. It's thanks to you that I was able to score so many goals in 2013. Even though I am going to Germany, I hope you'll continue to support me. Thank you."
Osako hit a career-high 21 goals last season for Antlers, with 19 of those coming in the J-League. He is regarded as one of the most gifted strikers of his generation along with Yoichiro Kakitani and Manabu Saito.
Osako missed out on the 2012 Olympics but played himself into Samurai Blue reckoning with a strong showing at the 2013 East Asian Cup. Osako notably bagged one goal and one assist in Japan's 2-2 friendly draw with Netherlands in November last year.
1860 Munich currently sit eighth out of 18 teams in the 2. Bundesliga, one rung below the Bundesliga.