The Chiba Lotte Marines announced today that they will stream Ni-gun home games at Lotte Urawa Stadium at Nico Nico Live (Eastern League and Challenge Match games). Streams will begin thirty minutes before the first pitch and end when games end. There will be no stream when games are canceled.
Source: Lotte announcement
[UPDATE 4/21 @ 4:56am]
The first Ni-gun game was streamed over NicoNico on April 20 and 24,828 fans watched Lotte take on Seibu.
Source: Daily Sports 4/20/2016