There has already been talk of a live action adaptation for Lupin III for about 2 years now, and that Arashi's Sho Sakurai will be in it. But Shun Oguri will be playing Lupin, which means that Sakurai will only be playing a supporting role, as Daisuke Jigen.
"TouSpo initially reported that Erika Sawajiri will be playing Fujiko Mine, and that Satoshi Tsumabuki and Norika Fujiwara will also be in the movie. But after numerous revisions with the planning and casting, it seems that they were finally able to start filming in Thailand this month. There's no changing the fact that Oguri will be playing the lead, but the bigger shock here is that Sakurai will only be playing second fiddle to him. This is an irregularity, as it is hard to imagine anyone from Arashi not playing the lead role in a movie." - (executive at a production company)
True, it's not far-fetched that fans will cause an uproar if a member of Japan's national idol group will only settle for a supporting role.
"But Sakurai is a huge fan of the Lupin series, and he was overjoyed by the offer. Even Jun Matsumoto said, 'I also want to be a part of this, even just a cameo'. These personalities probably already consider it an honor to be part of such a well-loved franchise." - (same executive)
But up to now, there has been still no official word that the live action adaptation of Lupin is indeed underway. A portion of the media has been reporting its authenticity because of the following reason:
"It appears that it's already being treated as 'official news' in Thailand. There has never been any official announcement in Japan about this project, but even Thai actress Yayaying uploaded a portion of the script on SNS and announced that she 'will be starring alongside the Japanese idol, Sho Sakurai' to her fan club. Even the producers seem troubled by these actions that have violated their confidentiality." - (showbiz pro representative)
And according to the executive above, "As for the other cast members, there's Taichi Saotomoe, who will be playing Goemon Ishikawa, and the candidates for Fujiko Mine are Masami Nagasawa and Kyoko Fukada. They still have not finalized yet who will be playing Fujiko despite starting filming, and it seems that things haven't been smooth sailing for them at all". The movie is reportedly set for a Spring 2014 release, as we all await an official announcement.