Spin-off of the popular Visual Novel "Steins;Gate". It is set up in a peaceful world line where okabe can hang out romantically with all the main characters of the original novel: Makise Kurise, Shiina Mayure, Kiryuu Moeka, Feiris, Suzuha Amane and Urushibara Ruka.
Okabe ends up in the Delta world line (>3% of divergence) after conducting numerous experiments with the D-mail.
When Okabe comes to, he finds the lab members preparing for a party and that due to successive experimenting the Future Gadget Laboratory's electric bill has skyrocketed. To compensate for this Okabe tries waitering and decides to sell the latest Future Gadget.
(Partially adapted from the Steins;Gate wiki).