シュタインズ ゲート 横行跋扈のポリオマニア
Steins;Gate: Oukoubakko no Poriomania Steins;Gate: Egoistic Poriomania
The setting is a few months after the end of the first season. On a calm day in Akihabara, Okabe and the other laboratory members are invited by Faris to go to America.
[Source: Steins;Gate Wiki]