Based on number of film appearances in 2016. Who else can it be? Suda Masaki with 9 films (2 lead roles). Surprisingly, he shares the title with Ikematsu Sousuke, whom he co-starred with in 『Setoutsumi』 and 『Death Note』 this year. Suda also did 2 dramas, 1 drama special, 1 online drama, and several guest appearances and endorsements. You workaholics.
By the way, Matsuzaka Tori ranks third with 6 films and Yamazaki Kento ranks sixth with 3 films (2 lead roles). It felt more with the latter because we also got to see him weekly for about 3 months.